I think this is a great book. Most developers should have it on hand as a reference. I say that in spite of the fact that I'm seriously annoyed by patterns fashionistas and Fowler fanatics.
This is not a collection of esoteric design patterns or capital-A architectures. This is a collection of tricks, schticks, and small-A architectures that just tend to show up repeatedly in the wild. Martin Fowler, with his perspective as an idea man and his position as a consultant and thought leader, has observed these and collected them together in a catalog along with some weighty analysis.
An initial read-through is probably a good idea, at least enough to assimilate the introduction and be familiar with the existence of most of the patterns. Out of real-world context, the material feels to me to be very academic and not very practical.
Where it comes together is when I can use the book like a bird guide whilst bird watching: Digging through some code or design docs and stumbling on a mechanism, conceived and implemented by an author who may not have ever heard of PoEAA, and having some recognition like "Hey, this is very similar to a Query Object pattern." Then I can go look it up. Sometimes it helps the task at hand by filling in as the missing documentation; other times it's merely "fun facts".
I've also used this book when putting together my own designs. It can provide useful guidance ("What's an alternative if I don't like our offline locking"). It can serve as a named reference ("By 'Value Object', we mean Fowler's rather than Sun's or Evans's").
In both of the above uses, the book shines when I have a pattern already in front of me and I want to know more. Probably as I get more practice out of putting context into Fowler's analysis, I'll be able to get direct practical value (rather than food-for-thought) out of working it the other way - starting with the academic discussion and being able to visualize real-world tailored specifics rather than idealized implementations.