st_aurafina asked for more explanation of the magic system in Death by Silver, and I've attempted to oblige:

If I had to describe the magic in Death by Silver in brief, I'd call it a steampunk version of Enochian, with "because angels!" replaced with "because SCIENCE!" as a more culturally palatable explanation for why things work. Like Enochian, it has an invented alphabet and an invented vocabulary and grammar, which we've combined with a system of sigil construction based on Cornelius Agrippa's magic squares. Unlike Enochian, there's no attempt to explain any of this as divine revelation; it's the work of very learned metaphysicists who developed the ideal system for modern and scientific magic.

It's worth pointing out to start with that this is specifically the system used by educated people in Ned and Julian's Victorian England. India and China have their own elaborately constructed systems of symbolic magic, with long histories and extensive scholarship about their theory and practice, most of which hasn't been translated into English. Other parts of the world have magical traditions that look extremely different. The Victorians, being Victorians, naturally assume that their system is the best, and exert pressure on colonized peoples to use it instead of their own traditional practices.

Even in England, there are both older traditions of folk magic and unauthorized experimental metaphysics, some of which is compatible with this system and some of which, rather spectacularly, isn't. That's "nonconforming magic," and you'll see more of it in the next book.

It's meant to be over-complicated, in true Victorian fashion, but you can break it down like this:

Orthography

The magical alphabet is 36 letters. Each letter also has a meaning, the first being "beginning" and the last "end;" we know from one scene in Death by Silver that "light" is the 31st letter in the alphabet. We haven't worked the whole thing out, although we probably will at some point, so really all you need to know is that this is true.

Vocabulary

The simplest metaphysical words are single letters with "end" added to them, for reasons that will become clear in a minute. So "light" = letter 31 "light" + letter 36 "end." Others are much longer and more complex, with the meanings of the individual letters usually contributing to the meaning of the entire word. It doesn't matter if the words can be pronounced -- this is a purely written language.

The metaphysical vocabulary is extensive, and is continually added to as modern life requires coming up with words for things like "omnibus" and "coal-gas." The Journal of Metaphysics publishes annual additions to the approved vocabulary, and you can look up new or obscure words in the Commons library. Metaphysicists like Ned are expected to know all the vocabulary dealing with common household problems, and to keep abreast of new useful terms, but figuring out what to call anything really off-beat is likely to require consulting a reference book.

Or can use generalizations, like "book" for anything from an unabridged dictionary to a pamphlet -- but the thing you're calling a book had better fit the definition of "book" used by the metaphysicists who worked out the vocabulary word, or you're likely to get unexpected results. Is a book a thing with pages, or a thing with writing in it, or a set of words? This is what metaphysicians go to school to learn, and what metaphysicists spend their time debating and writing papers about.

Grammar

The basic form for enchantments is "verb + object": "bring light," "remove ink," "repel water," etc. You can add adjectives or possessive pronouns as specifiers: "remove metaphysical words," "gather together same color," "hide my tracks," or extend sentences with more complex grammar.

Where this gets interesting is when you start layering one enchantment on top of another, because you end up with something like a multi-dimensional word puzzle; verbs in one enchantment will create sentences with nouns in another enchantment, and you'll get the result of that sentence as well, which may be intentional or very much not.

So, you have an enchanted umbrella that's supposed to stay dry. It's enchanted with "repel water." You can test for the verb used in the original enchantment by using the noun "light;" it will momentarily form "repel light," the umbrella will look like it's sitting in a dark shadow, and you can say to yourself, why, yes, that's an enchanted umbrella.

On the other hand, suppose you're a forgetful metaphysics student, and you know your enchanted umbrella is around here somewhere, so you try "bring umbrella." First of all, this is a bad idea because the energy involved in making your umbrella come to you will probably leave you too tired to go anywhere; more on that in a minute. Second of all, if you're lucky, "bring" will catch on "water," you'll get "bring water," and when you find your umbrella, it will be soaking wet and sitting in a spreading puddle. If you're unlucky, "umbrella" will catch on "repel," your umbrella will try to repel itself, and you'll very quickly learn where your umbrella is -- or rather was -- as it rips itself to pieces and covers your parlor in shredded umbrella parts.

Especially with more complicated enchantments, you may also get tangled grammar, where two (or more) enchantments have merged to form one horrible ungrammatical sentence, and the enchanted object now doesn't do anything, or does random undesirable things.

Sigils

To actually do metaphysics, you write the enchantment, either on paper or in the air with a wand. Metaphysicians will tell you that a certain type of wand is ideal, and metaphysicists have written a lot of words about the properties of various types of woods and metals, but really you can use a stick, or a pen, or a knitting needle. People get very attached to their wands, but that's about the same level of grounded in truth as saying that you can't write without your pen (your pen, your special pen.)

However, rather than writing out the entire enchantment, enchantments are shortened by converting them into sigils. Here's how you do it:

First, pick a magical square. Each one corresponds to a planet, and sigils are typically formed using the square that corresponds to the planet that corresponds to what you want to do. If it's a love spell, you're using the Square of Venus. If it's a prosperity enchantment, you're using the Square of Jupiter. When in doubt, you can use the Square of the Sun for almost anything.

Each square is made up of numbers that add up to the same total in each direction. To draw a sigil, you visualize each number as corresponding to a letter of the alphabet, and then spell out your words by connecting the "letters" in order. On the squares with more than 36 numbers, you can ignore the ones that are higher than 36. On the squares with fewer than 36 numbers, each number represents more than one letter. If you look at the example about halfway down this page of how the sigil of Hagiel is constructed on the magic square of Venus, you'll get an idea of what I'm talking about.

Most of the time you're just visualizing the square, not actually drawing it out. Intent matters here as much as anything. Julian has a bad habit of drawing sigils that in fact look like "crabbed squiggle," but it still works because he knows what letters his sigil is supposed to be connecting.

Limitations

Enchantments done according to this system have certain limitations. They can't create things out of thin air or make things vanish without a trace. They require energy on the part of the person casting the enchantment, which is why a lot of things are impractical to do with metaphysics; it's usually far more exhausting to move your bookcase by metaphysics than it is to get up and move your bookcase (although I imagine there are disabled metaphysicians who have "how can I use metaphysics to move objects with the least effort and greatest results" down to an art.) That can be partially counteracted by doing an enchantment over a period of time. They can't be done instantly: you at least need time to visualize and sketch the sigil, which is hard to do if you're being punched, falling off a cliff, or running for your life.

Laymen

Most people in Ned and Julian's world have no clue how any of this works, any more than most people who use a computer understand how a computer works, or than most people who take medicine when they're sick know how the medicine works. The wealthy hire metaphysicians to do their household enchantments for them; the lower middle class and most prosperous of the working class buy commercially enchanted objects; the poor buy badly-enchanted objects, or second-hand ones, or go to back-alley magical practitioners.

The majority of Ned's job is enchanting household objects so that they'll do what people want them to do (stay clean, repel water, protect against fire and burglars, etc.) correctly and without unwanted side effects. Most of the rest of his job is dealing with household enchantments gone wrong, either because two enchantments are conflicting, or because something was badly made, or because something has worn out. And starting in the second book, he's going to be spending more of his time working for Hatton, where he'll be investigating the more criminal uses of metaphysics.
Was that helpful? Or at least entertainingly confusing?