Heck no, it is very far from random. The approach is a special application of general retail layout practices, which you can learn about in Paco Underhill's classic "Why We Buy." I highly recommend reading that, and his more recent book "Call of the Mall." I don't know of a book that talks about bookstore layouts specifically, but once you understand the general principles, you'll spot them at work in bookstores as well.

Beyond the obvious functional division into sections (business, romance, hobbies...), and giving the new prominence over the old, there is a lot of hidden psychology driven by the problem of maximizing revenue per square foot per month.

For example, you put the high-margin items at eye-level, and older backlist stuff lower down where you have to crouch. Survey firms like Harris Interactive will run studies for you with different display configurations and shelving tactics (they now have new technology that allows them to run experiments virtually, through simulated shelving).

You put up big displays of single books like Harry Potter which have the power of major marketing, PR and word-of-mouth behind them. You don't want to pass up an obvious sale opportunity because you forgot to remind a primed customer that he/she wants the latest Harry Potter. You ESPECIALLY don't want to lose out on the higher-margin hardcover phase of a traditional book, because once you get into the paperback phase and later reprints, margins shrink.

Impulse purchases and non-necessary stuff is up-front, so you have to walk past it to get to the stuff that you generally go very purposefully to buy (like genre romances and mysteries, which are addictive, so you are going to find your favorite author wherever he/she is buried, so they might as well tempt you with stuff along the way). This is an application of the "prescription counter at the back of the drug store" principle in general retail.

Stocking-stuffer type little gifts and small books are closer to the checkout for the same reason candy is near the checkout in grocery stores.

Tables and aisles are spaced carefully so customers don't bump into or brush against each other too much. For purchases that need some browsing, this annoys people and interrupts their browsing, making them move on to a less crowded section (this effect is called the 'butt brush' factor and was discovered by Underhill's researchers in necktie displays in clothing stores).

Kids' and music sections are way back because they tend to be places where people spend a lot of time. You don't want them in the way of foot traffic that's moving along more briskly.

Books ARE different from general retail in some ways though. For general retail, you either optimize for experience (premium, high margin items, where you can survive on low conversions) or velocity (low margin items where you must move product fast to get revenue). Both are driven by the economics of churn. You move slow-movers out, and replace with fast-movers when you can. Even in premium. In general retail, variety and selection are important but not as critical.

In books though, "economics of scope" is at work. If you don't have a fairly high probability of finding nearly any reasonably new and non-obscure title, you'll stop visiting. It's not like buying milk. In a book store, one day you might want the newest Harry Potter (milk), but another day you might want a more obscure book that's a couple of years old (more like an artisan cheese). Those are somewhat weird expectations to work with.

So the stores do have to stock far more "variety" than traditional retail stores with equivalent amounts of shelf space/inventory. It is naturally a long-tail market, which is one reason why it has been so quickly disrupted by online shopping.

All this is changing rapidly of course, due to eBook sections in places like Barnes and Noble, and the impact of the coffeeshop corner.