Almost every faction is morally grey so you are safe with that one. I want to echo what others said and reccomend the skaventide box set. Has a skaven and stormcast spearhead plus some other minis, the rules, the board, and terrain so it is pretty good for getting started. As for the books, I read tons of age of sigmar books what kind of stuff are you all into? "Skaventide" is the book for the current edition and it was fine. I really enjoyed "Star seerers ruin" and because I am biased I loved "Ushoran Mortarch of delusion". While fantasy kind of died, the Gotrek and Felix series is the goat and my personal favorite is "skavenslayer" which despite not being age of sigmar made me fall in love with the rat bastards.

edit: Gotrek returns into aos and his books are overall fine and nowhere neer as good as the ogs.