In Thin Air, Robert B Parker deviates from his normal mystery format and produces more of a thriller. What happened and who did it is never in question -- the issue is what will happen. While this is being resolved, Parker reveals rich details about the principal characters, keeping the reader engaged throughout the entire book.
Viewpoint varies with the primary chapters, as usual in the Spenser series, from the detectives perspective. Between these, the victim Lisa's view is represented. This is quite nicely pulled off.
The welcomed trend in the series of deemphasizing the tiresome participation of Susan in the primary plot continues with Thin Air. Additionally, giving a rest to the use of Hawk as a superhero to completely suppress any opposition is also welcomed. While Hawk is a very enjoyable character, he's overused in the books preceding this.
So Thin Air is highly recommended. If there is one criticism, some of the action at the end strains credibility to the point of collapse. But the reader is still touched by the result, something which can't often be said for genre work. This book only reinforces my assessment that Parker is an excellent writer.
Dan