It sparked some thoughts so I had to reply, click over to read his blog and my reply:
I'm the same way. I get very nervous choosing a new book to read. I don't like to start something and have it turn out to be a dissapointment. I've gotten lucky plenty of times, and in the case of "Song of Ice and Fire" it was by a store clerk recommendation. I didn't know the guy, but he had such an apparent affinity for the WoT books (of which I was purchasing one at the time) that I thought, "Maybe he knows what I like."
I think it all goes to wanting to read a certain kind of book. When we have read something enjoyable, we want to recreate that experience again, though we don't want it to be the same. Seeking that out can lead to dissapointment, and I have many times gone bookless for a while debating what to read next. This has also led to many re-reads of favorites. That said, it is very fulfilling when you read something you wouldn't have normally, only to find that it is INCREDIBLE. For instance with "Song of Ice & Fire" (isn't there a handy acronym to use? SoIF?) I wanted swords and sorcery. Though entranced by the story and initially promised some supernatural presence, I began to wonder, "Where's the magic?" I'm certainly glad I didn't put it down. The politics of the series were something I had never read (Wheel of Time comes close at times), and certainly expanded my imagination.
In answer to your question, as to how to better choose something new...I - have - no - idea. But if you figure it out, I bet you can use that to better sell your own books/stories. I suppose I do have one idea: Word-of-mouth. But we already knew THAT.