[Koha] data import; where to start?

Hello. I'm hoping to import quite a bit of book/author data into Koha, and I'm not sure quite how to go about it. I had started writing a script to pull records from one database, reorganize them, and put them into Koha's database... but I don't know which part(s) of Koha's database to dump them in (or if this is even a good way to do it). It seems that some parts of the db are generated from other parts, but I can't tell which are which. So, any idea where to start? Should I use an existing tool? Learn all about MARC? Submit data through the web interface instead of directly to the db? I don't mind writing a tool to do this, but I'm not sure what direction to proceed in. -- Scott