"A primer on a person would provide you an introduction or overview of his work, enough so that you would get the gist of what he was all about."
Okay, then I recommend that one read his books, you will soon understand what he was about. And a Google search should provide much more information quickly, but to me that would be irrelevant, let his work be his statement of what and who he was.
I read most of his books and three remain in my library for another read every so often; "Abbey's Road," "Desert Solitaire," and "Down the River." Some of his stuff was a little too eco-terrorist for me, but those three books are well written and I enjoy them a lot.
I will warn you that Abbey was curmudgeonly, like me, so that is one reason why I like him. Because he was in the news a lot I remember much about him. His personal life was a mess, so someone might make a judgement and not read him. That would be a shame.
So read the books and you will know exactly what he was about. Most are short and can be read in a night or two.