There is a good trick that may help you find the book you need or at least improve your chances.
The way it works is this; the lvl of any book that drops is determined by the lvl of the mob that drops it. So, if you want a lvl 28 book, you'll need to kill lvl 28 mobs. And the easiest way (I know of) to find a lot of lvl 28 mobs that drop chests is to take a lvl 28 character into Splitpaw for a solo run through the upper tunnels.
Since Splitpaw scales to your level between 20 and 50, you can take a lvl 28 character through there and you will see mostly lvl 28 mobs. I find that a solo upper tunnel run takes me about an hour and yields an average of a dozen chest drops. It will also net you about 20% of a level in XP so you should be able to make about 5 runs before you hit lvl 29. Of course you could always turn off your combat XP and give yourself an unlimited number of runs to complete the task. In any event, have fun!
P.S. - here in EQ2, it's a broker, not an auction house!