How many employees/books do you have? I know it sounds pretty arcane :), but we actually set up a small book/video library with checkout cards. Works pretty well.
I have the same problem.
3.5 GB of book, all formats (pdf,chm), some times i have ISBN and picture.
I don't know what can with all this materials.
If I assume that your team works based on confidence (and the contrary would be very surprising), then why don't you use an Excel sheet on a shared drive? You probably don't have so many books and so many employees that you need a real database to handle all of them. Of course, this requires a little discipline. But you need that as a developer, anyway ;-). Several other tracks: a simple web service combined with an InfoPath form (nice little application that I would be very happy to develop just to learn new stuff :-); or FlexWiki with a topic for each book; or .Text with a feed for each book :-); ...
I know this is not *my* company, but... As a demonstration of what SharePoint is capable of, as a consultant, I created a simple book library management system using a custom list in SharePoint. Because there is no limit to the number of views that can be created against a list in SharePoint, and since security is flexible, I was able to create a means of allowing users to see at a glance which books were1 available, which were checked out, to click on a given book to create a reservation for it to be picked up at a later time, etc... Since this was just an example, I was not around long enough to see how it has worked over time... However, I do think that SharePoint could serve this purpose. Not free of course, but if your company already has Windows 2003 licenses, then it is included...
I'm sure this isn't what you want to hear, but if checkout & categorization are the basic requirements, I would think you could build one quickly in Smalltalk hooked to a simple db.
At the time we had a big-assed Excel document on a shared folder. :P
Why don't you go to IKEA and buy a bookshelf. Then put a sheet of paper on the side or top of the bookshelf.
When someone takes a book out, they write the book title and their name down beside the book title.
When they return the book, they cross the entry out. :)
cut each page out of each book and use them to wallpaper the corridors.
that way everyone can browse and you'll never lose any.