I just submitted the first book review I've written in years, and certainly the first since my own book and those of my friends started accumulating reviews.
It's a different experience. First, I'm more aware that writing reviews both is and is not something I have to do. On the one hand, it adds nothing of value to my C.V., and time spent reviewing is time I could spend elsewhere. On the other hand, it's an important service, and if I accept a review it's an obligation like writing a recommendation letter or reviewing a manuscript: something I just have to hunker down and do--as much for myself as for the sake of the author and journal.
(The reason it had been so long is that one of my last reviews was a terrible experience, and entirely through my own fault: I shouldn't have accepted the assignment or agreed to the deadline I did, and it became a months-long saga of guilt and resentment. I hated every minute I spent both writing and not writing that review, and probably burned a professional bridge in the process. Part of the reason I accepted this review was to reset my attitude.)
Here's what I've learned:
1. As a reviewer, your name will be attached to this book for as long as the Internet lasts
When I reviewed books in the past, I figured the author would probably come across it, but I never thought of myself as writing for her--I was writing for new readers! But authors get copies of their reviews from their publishers, and some even (ahem) Google their books periodically to see what kind of notices they're getting. I can assure you that I know the name of every person who has reviewed my book.
That doesn't mean you can't give an honest review--if you can't do that, you should decline the assignment--but I think a lot harder now about a) what truly counts as constructive criticism for the author, and b) what a casual reader might need or want.
2. Most people don't read a standard 750-word review very carefully
This is a corollary to the above. Unless I'm the author or she's a friend of mine, I just want to know the basics of what the book is about and whether it might be worth picking up a copy.
3. Most reviews aren't things of great beauty, and that's fine
A book review in a scholarly journal is meant to be a functional thing. It summarizes, it contextualizes, it offers an opinion about what's worthwhile or original.
For me, the task of writing a review used to feel paralyzing: it seemed impossible to write interesting prose while also conveying the author's argument accurately. I was terrified that I wasn't qualified enough to write the review, or that I'd misrepresent it or get some major details wrong. Now I know that lots of reviews do get things wrong, or at least askew, while some of the most useful ones read like an awkward pastiche of the author's own words.
4. Most books don't get a lot of reviews
Scholarly books aren't like trade books. There aren't a lot of venues that review them, and many publishers send out only a handful of review copies. So if you're an expert, and you're solicited to review a book and decline, it's possible no one else will review it for that journal. That's not necessarily a reason to accept--your time is valuable--but being a member of the scholarly community does come with obligations.
5. A review is a service
You do the best job you can. You bring to bear your expertise, and you try to be fair, but the review isn't about you. If you're using a 750-word review to show off your superior knowledge, or your prose style, or your witty put-downs, you're doing it wrong.
The review I just completed was for a book on the fringes of my area of expertise, but its subject is something I'm genuinely interested in (and that turned out to be more immediately relevant to my second book than I expected). It also felt like it was time for me to get back into the reviewing game. So I approached this assignment the way I'd approach a recommendation letter: I blocked out time to read the book, well before the deadline, and then I blocked out about 48 hours to write the review. I didn't dilly-dally, I just wrote it.
I could have done some things differently, and I likely could have done some things better--but it's not worth overthinking. More importantly, the process was enjoyable enough that I'll probably do it again the next time I'm asked.