Part of the problem is that not much actually happens between Hobbit and LoTR. There's some shifty Cold War stuff between the White Ccuncil and Sauron, Aragorn running around getting muddy throughout Middle Earth but not really getting anything done except protecting hobbits... Balin's re-invasion of Moria is the biggie, but to dramatise that would take a lot of the depth out of the Moria bit in LOTR.
That's the problem with the books - the history stuff was all meant to be backstory, so that Sam could run around screaming 'Elbereth' and it would seem fitting. If it all gets documented in detail, as has happened, then all we've got is yet another bltatantly nordic-slash-judeo-christian mythology with the light shining through the gaps.