On average, I will buy one or two programming books per month. The choice is usually based on whatever happened to pique my interest that month. Only a handful get read cover-to-cover each year. The rest I will either give up on because of disappointment in the content or I will skim from time to time if I think it has something interesting or useful to tell me.
I’ve also learned to screen books based on publisher. All other things being equal, I will usually go for an Addison-Wesley or O’Reilly book. I won’t even consider Wrox books anymore.