Ecology of the Planted Aquarium is one of my favorite books out there, but yeah, it does read like a textbook. It's one of those books in which you can learn something new every time you reread it.
Kasselmann's two books (Aquarium Plants and Planted Aquariums) are both good reads too. The Encyclopedia of Aquarium Plants (by Peter Hiscock) is an excellent beginners book and has all the info you need to start up.
And like Darkblade said, Takashi Amano's Nature Aquarium World books are the best inspirational books for aquascaping, if you can find them.