Getting your hands on good information for Heathenry is difficult, for a few reasons.
The problem with a lot of easily-accessible sources is that they are heavily peppered with subjective interpretations and put together by people who aren’t, at minimum, well-read. You don’t need a doctorate to know what you’re talking about, but you do need to know how to collect, sort and interpret information. (Which, incidentally, are the skills that get you degrees.) Anyone who doesn’t have those skills is a questionable source.
But resources put together by people with these skills tend to be locked behind paywalls or out of print. So what are your options?