NASA just released two free E-books on the Hubble Space Telescope and it's yet-to-launch successor the James Webb Space Telescope. Both E-books are packed full with interactive features that let readers watch such things as galaxy collision simulations, and manipulate a telescope model between pages.

The Hubble, which launched in 1990 is set to come to its end of life cycle in 2013. The space-based telescope has no doubt supplied us with some of the most interesting images ever seen by mankind. It's replacement, the James Webb is almost three times the size of the Hubble and will continue the tradition of bringing breath-taking images to us here on earth.

"These new e-books from NASA will allow people to discover Hubble and Webb in a whole new way - both the science and the technology behind building them," Amber Straughn, an astrophysicist on the Webb telescope project at NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement. "They collect all of the amazing resources about these two observatories in an excellent product that I think people will really enjoy." The ebooks are available at the Apple iBookstore or can be downloaded as a PDF here.