There is, in fact, nothing very difficult to grasp about any part of a submarine torpedo tube, if those who study them do not attempt to understand them all at once.
This pamphlet, as has been said, is a torpedo tube primer, and not an engineering treatise; it includes nothing "over the head" of the beginning student of submarine torpedo tubes.
I'm a major fan of old technical books on just about any subject. I recently picked up a pair of books from the late 19th C on the care and operation of steam engines. Very cool for the retro-geek in me.
Also noted on BoingBoing.