Translating a book into a TV show is always tricky, as we all know. Three reasons why:
1. TV shows are more constrained by time than a book is.
2. Every fan of the book will have some internal idea of what a character/setting/etc. should look like, and you can't please everybody.
3. The First Season of any TV show will be received well if it's done well. But that just builds up the expectations for the second season ... and the third season (if there is one) ... and if you don't meet people's expectations, they blast you online, etc.
I haven't seen American Gods, so I'm prepared to at least give Neil a chance, here.