The Monster Manual V is the kind of book you can set down for a while and then pick up again and not miss a beat. For that reason, I've been reading it for quite a long time, but I finally finished it today when I went out to my car for a "lunch" break.
You'd think that the monster manual concept would be played out by the time they're on number 5 (and if you count the Fiend Folio and the smaller Monsters of Faerûn book, they're really on 6½, not 5.) However, that wasn't the case at all. The Monster Manual V was quite a good book, and in fact I enjoyed it quite a bit more than Monster Manual III, which I read not that long ago as well. It's a lot of really good monster ideas, and I really like the implementation of them.
There's fewer than in some monster books; each entry took at least two pages, because they spent more time talking about the monsters, their role in the ecology and campaign, a few strategies, etc. These still weren't as flavorful and inspirational as Privateer Press's Monsternomicon series, but it was a darn sight better than the original Monster Manual. It really made the signal/noise ratio for this book fairly high, I thought... I could immediately see where I'd potentially use most of these monsters, rather than just kinda gliding over them saying, "meh." The concepts were, somewhat surprisingly, useful, not weird esoteric ones. In fact, some of them, like the Wild Hunt, are so iconic from folklore and mythology that it's almost embarrassing that it took so long for them to get done. Even the less "creative" ones, like variants on hobgoblins and kuo-toa so you can throw an entire society at the PCs with very little work, were interesting reads and potentially very useful entries.
All in all, I can recommend this book highly, moreso than most of the other monster books in the 3e/3.5 line-up (you still really need the first Monster Manual though; it's got too many of the basics). Now that it's finished, I'm replacing its slot in the line-up of "what I'm reading" with Sandstorm, the environmental book that focuses on deserts.