One recommendation, and one meta-recommendation: The recommendation: Mr. Neighborly's Humble Little Ruby Book. Short (maybe 150 pages). Meta-recommendation:

One recommendation, and one meta-recommendation: The recommendation: Mr. Neighborly's Humble Little Ruby Book. Short (maybe 150 pages). Meta-recommendation: Get a copy of Anki (free), and as you read, make new cards that test a single piece of knowledge (this can mean you make two or three cards for one concept...so be it!).