Hubble Space Telescope Discoveries is a 900 MB tome which discusses the stellar phenomena discovered by that more than two decade old satellite. It includes videos, interactive demos, and extensive image galleries.
This ebook is the work of the Space Telescope Science Institute, and it is one of 2 titles produced in Apple's proprietary iBooks format. You can find these titles as non-interactive PDF versions of the ebooks here.
The other title released last week, James Webb Space Telescope Science Guide, focuses on NASA's newest telescope. This ebook is only 500MB in size and focuses on what the construction of the telescope and what it expects to see when it is launched in 2018.
Cool fact: This satellite will actually orbit the sun, not the Earth, and is planned to be deployed to one of our planet's Lagrange points. The plan is to have it orbit in the L2 point, which would keep it permanently in Earth's shadow. This telescope is going to be used to detect dim and distant objects, and blocking out the light of the sun will make that task much easier.