One of my favorite books, though I take umbrage with every single edition of this book until the end of time advertising it as a "Hannibal Lector Story." All he does in this book is rage bait Will Graham! Either way, an incredibly entertaining mystery thriller written in a very active and engaging style; frantic and furious during time-sensitive plots and investigations, but not afraid to slow it down and reflect when the night sky is out and all is quiet. If you are a fan of Manhunter (as I am) you will easily find, surely as Michael Mann did, the noir beauty of this thing.
Speaking of movies, it pains me to say it but: the Brett Ratner movie did the ending better. When I realize this fact it makes me sick, makes me want to puke, I'm not entirely sure what to do with myself. But it's impossible for me to deny. Dollarhyde's attack on the Graham's in the book is like, A page. It genuinely feels like that Thomas Harris was sitting at his typewriter, confident his book was done done - only to nearly fall out of his fucking chair realizing he forgot to resolve Molly's whole plotline. It comes off noticeably rushed; I would not believe my eyes if I read that this was how Harris intended it. The BRETT RATNER film more effectively sets up the finale and pays things off in a more narratively successful way. God, I'm gonna go throw up. The final pages of Will's nihilism over nature's indifference to killing feels kind of mixed when the rest of the book had displayed the grave and ugly nature of killing even when you don't see any better option. The endings of both films, though considerably more clean in how nice they end for Will, still seem more in line with what the book seemed to be gesturing at. Having Molly pull the trigger was smart narrative construction, but everything surrounding it just felt way too much like Draft #1 of that scene.

Harris has never got enough praise as a stylist. When he launches into the 'high' style (often, as you say, when he's reflecting on events) his voice is pure poetry. I would take this and SOTL over 999/1,000 "respectable" novels any day. He has that ultra-rare quality of being interested in everyone and everything. When I read him I feel acutely envious that I don't see the world the way he does.
The way he writes really sets it apart from any other 'procedural thriller.' it has a very pointed intensity that is from another world. I'm immensely excited to check out the rest of his books. (not a lot, sadly. and one of them is Hannibal Rising.)