Technically, The Pure in Heart is almost as strong as The Various Haunts of Men. Hill uses the same multiple 3rd person POV technique again and it still works, though for some reason it was vaguely less effective. Once more, the reader is drawn into the lives and minds of the characters, all of whom are realistically drawn. But....
There's something missing and it took me a little while to figure out what it is. The book lacks a central sort of heart - a sympathetic central point of view. In The Various Haunts of Men, that heart was Freya Graffham, who, for reasons I'm not going to get into, does not appear in the second book. Now, instead of Graffham, we are given Simon Serrailler, whose point of view was the only one never given in the first book. Simon was always either observed or talked about, but his point of view was never breached. This made him something of a cipher and very compelling. But he was compelling because Freya found him compelling. She convinced the reader to find him so as well. Left on our own with Simon now, he's not so much compelling as as inaccessible and hollow. Hill obviously still finds him a very attractive character, but without Freya's eyes to soften the portrait, he's just rather frustratingly cold.
The story itself also lacks something. The Pure in Heart is much more procedural in nature. We see the Lafferton police rally to search for an abducted boy, or solve the murder of a handicapped woman and both are not uninteresting. But the taut line of suspension that runs through The Various Haunts of Men just simply isn't there, so the climax is less of a catalyst and more of a get-it-done sort of experience.
Though well written and interesting to a point, The Pure in Heart is a lesser book than its predecessor. The Various Haunts of Men is most definitely the one to read. I wouldn't necessarily bother with The Pure in Heart unless you're a hard core fan of procedurals and crime fiction, or you're a sucker for inaccessible, emotionally distant men.