For those who would rather own
a copy instead of borrowing
the images and links will take you
to booksellers.
Barnes and Noble has a large
selection of mostly
new books. Check out their
sale annex where you can get
new or in new condition books
for less than $10.
For a wide selection of used
and hard to find books
try Alibris. They are mostly
a network of independent
bookshops. Often they
don't have the ISBN of books
so you have to do a keyword
or title search and then
pick through a list of
unrelated books to find
the one you want.
Willman Bell publishes
alot of independent
astronomy books as well.