I don't find the jQuery API to be particularly friendly. It tries to be cute and ends up being annoying. Its implementing code is also an abomination, so not particularly helpful. I'd rather read through Gecko internals than try to figure out what the hell a jQuery helper actually returns.
The DOM is at least very, very well documented. jQuery has documentation, but it's not even close. It gives away what jQuery always has been, which is a library that is aimed mainly at assisting bag-of-tricks StackOverflow programmers than people who actually want to understand their programs and the object graph they work on.