Here are some of the books on my shelf that I recommend:
"Scent and the Scenting Dog", by William G. Syrotuck
"Practical Scent Dog Training", by Lue Button
"Search and Rescue Dogs, Training the K-9 Hero, 2nd Edition", by ARDA
"READY! The Training of the Search and Rescue Dog", by Susan Bulanda
Although these others are for more specialized types of training, they contain information that would be useful to any search dog handler:
"Training the Disaster Search Dog", by Shirley M. Hammond
"Avalanche! Hasty Search", by Patti Burnett
"Cadaver Dog Handbook", by A. Rebmann, E. David, and M. H. Sorg
Here is a quote from Lue's book:
"Is extensive reading a good idea? Shouldn't the various theories be studied? It is probably better to do your reading after you train your first scent dog."
I understand what she means by this, because you can read all these books cover to cover and still not be able to read your dog. See if you can observe SAR trainings to watch experienced handlers searching with their dogs, that is the best way to learn.