Oh my stars! Here’s what they mean:
5 ★ → FANTASTIC. Standing ovation. Sending copies to friends.
4 ★ → Really liked it. Might even gush over it a bit.
3 ★ → Decent read. Not great, but not bad either.
2 ★ → Not for me. The bad outweighs the good; would not recommend.
1 ★ → Painfully bad. Would feel guilty donating it.