I don't go to big bookstores often because there isn't one in my town and the nearest is eight miles away. Not a great distance, mind you, but I don't like wasting other people's gas to get there (me driving? Madness!), so when I do go to one, I do it with the intent of buying as many books as I can afford.
Except when I don't. I rolled a natural one the other day. I voyaged to a Books-A-Million with the intention to buy some science fiction, or failing that, fantasy. Currently, there's an imbalance between the two, with the latter having the superior numbers, so I was looking to fix that and sate my scifi cravings. Unfortunately, they didn't have any scifi that piqued my interest, so I moved on to fantasy and found much the same. I don't know if its just the two stores I've been to, but Books-A-Million flops when it comes to having a decent selection of scifi/fantasy. They'll have several books by an author that I might want to read, but never the first book in the series. Truthfully, I've found that Barnes & Noble tends to have a better selection of scifi/fantasy, while Books-A-Million has a better selection of graphic novels.
Then there's the physical quality of the books themselves. Look, I can tolerate a new book having some dings to it, because hey, that's the perils of shipping and handling, but I am sure as f#ck not going to buy a brand new book that has a piece of the spine missing or a bent up cover. Here's an example of what I'm talking about: I've been reading L. E. Modesitt, Jr.'s Imager and was going to buy my own copy (I'm reading the library's) along with the second book in the series. Then, I looked at the spine - specifically, the corner where the cover and spine meet - and it looked like someone had taken their nail and scrapped off a piece. There was other damage to the book too. Unfortunately, BAM doesn't keep any extra copies in their backroom, so my only recourse would have been to have them order a copy for me and I really didn't feel like going through with that. I mean, if this had been a thrift store or a yard sale, I would have bought the book without giving it a second thought, because then it would have been a used book, but I'm not going to pay for a brand new book that looks like it's been mishandled.
There were a couple other books I considered, but by that point, I was feeling a bit deflated, so I bought a book for my mom instead (she's recovering in a nursing home/rehab center from something called a T.I.A.), so it wasn't a total loss.
There's a small indie bookstore downtown that I've ordered books from before, so that might be my future mode of procurement, since I can't rely on a chain store.