"X-15: Extending the Frontiers of Flight" a Free E-Book from NASA

NASA is offering the book X-15: Extending the Frontiers of Flight by Dennis R. Jenkins as one of their small library of free e-books for most popular viewers. (Thanks to NASA Watch for pointing it out.) Personally, while e-books may indeed be the future (at least until civilization next stumbles, and they – trapped in their unusable viewers – all become inaccessible for a few centuries, if not