We have every Springer book from 2005 to present, full-text online. This includes book series, encyclopedias, etc (even class textbooks). On every subject discipline, not only math. Springer is probably the most important publisher of all STM (science/technology/medicine).
So if you are looking for a math book and it was published by Springer in or after 2005, then Springerlink is where you will find it.
You can print out any page, chapter, or even the whole book. Or purchase your own personal paperback copy from the specific book's webpage, for $25.
We are continuing this e-book purchasing with Springer. After all, why purchase 1/3 of their catalog in print format, when you can get their entire output, electronically, for about the same price?