I think it's worthwhile to use the L2, at various stages, to learn other things, because that info-seeking can be a motivational tool and a recreational one (I know I prefer nonfiction to fiction, in general... I once spent a year trying to read a new book each day, and 2/3 was 'elective' nonfiction... after summer vacation was over, I ended up only reading the equivalent to 4-5/week, and I retained a relative fraction compared to if I hadn't given myself a deadline, but it was so worth it--but I digress, this relates to my info-processing vs. info-retention pet theories that I've since conflated in Anki).
For the more functional, intermediate to advanced stages, there's also the differing perspectives, in some fields, that you can only really access in the target language. That's one of my main purposes for learning multiple languages. For example, I have an interest in a particular country's particular area of history, and after a certain amateurish period of research+paper-writing, I grew tired of only accessing secondary sources, or relying on whatever some other researcher decided to find and translate for me (I consider a translation of a primary source to be a secondary source regardless, as there is a mediator (or more) interjecting their own interpretation(s), however closely they attempt to adhere to the original). History's just one example, I can think of equivalents in other fields, and ironically it's our growing 'connection' and translation abilities online that gives us this 'negative knowledge' of what we don't/can't know, but we know it's out there, 'in the raw'...
Have you seen those マンガでわかる books? The Manga Guide to Statistics, Molecular Biology, Physics, etc...
http://www.kenleewrites.com/2010/03/man … books.html
http://timmaughanbooks.com/2009/06/07/t … 09-review/
Last edited by ruiner (2010 March 11, 5:12 pm)