I used this workbook to learn hiragana in just a few weeks. It teaches you how to write and use hiragana and is almost perfect for beginners, except for a few important details it just decides to leave out.
This teaches hiragana in small batches, giving detailed guides for stroke order, direction, and how to end certain strokes (trailing, abrupt, hooked). It does not mention that some hiragana may look different in print than they do written. Despite this omission, it occasionally uses some of these characters in the exercises. If you're unaware of this custom, it'll seem like they've thrown a secret hiragana at you.
After you practice writing your new hiragana, it gives you a number of different exercises to help you become familiar with their use. As you're introduced to more hiragana, the previous ones are included in the exercises to reinforce what you've already learned. When you run out of new hiragana, it moves on to dakuten, hadakuten, and yōon, and after that it has you writing full sentences in hiragana without a peep about how you're probably never going to do this outside of a hiragana workbook.
The book covers long vowels, including the tricksy long O, but doesn't bother explaining you probably won't have to deal with this much in the real world as these sneaky double Os are usually written as kanji and so for certain words the problem of whether to use a う or an extra お isn't likely to come up.
It's also of the belief that ん is always transliterated as an m before p, b, or m, and teaches it as law, except this is not always the case. My romaji dictionary, for example, doesn't follow this convention, which might make it difficult to look up certain words if you're unaware of this peculiarity.
The exercises don't have an answer key, which frustrated me more than once as I couldn't find some of these words in the dictionary—see above—and even if I could, they were often written with kanji so I couldn't see if I was right with some of the more tricky problems. There is a short review section at the back that provides answers, though, and it's a nice way to gauge how well you've picked up the system.
Because the usage rules are slowly dispensed throughout the lessons and you're not hammered up front with a bunch of information you can't use yet, the book feels very approachable. There just might be some confusion later when things aren't as it said (or didn't say).