I've already done an article on how to relist items for 99p, but of course there is more to it than that. Like making sure you can list the item for 99p and still make some sort of profit.
The point is that a lot of books cost more than £2.75 to post and that is where Ebay has capped the postage charging. For modern fiction (hardback and softback), Ladybird books, small children's books and several paperback books this doesn't matter.
The trouble is when you get into collections of books, encyclopedias, books in slipcases and hardback versions of graphic novels. If you price these at 99p you won't cover the costs at all, let alone profit from them.
The only real solution is to continue to price the item higher, even though it won't be free-otherwise its a false economy. You do need a number of books, etc. which are light enough to be sold at 99p.
(Of course hopefully things do not sell at 99p-you're just listing them at that price to save on listing and relisting costs).
And of course with expensive items that just won't sell it isn't practical to sell at 99p.
The trouble with this price-capping is that Ebay is trying to please the sellers and the buyers, but seem to have not solved the problem.