Where can I learn more about Scrum itself?
If you would like to learn more about Scrum itself, as a method, we warmly recommend the book "Scrum and XP from the Trenches" by Henrik Kniberg. It's the best book we know about Scrum, and maybe the only one you'll need. It's available as a free download.
Also, you should watch this awesome video by Henrik Kniberg, although it's more an introduction to agile thinking overall, not to Scrum specifically:
If you're looking for a concise definition of what Scrum is, take a look at "The Scrum Guide" by Ken Schwaber and Jeff Sutherland, the creators of Scrum. It's the definitive reference on Scrum, but quite dense.
Mike Cohn also provides useful learning material about Scrum and agile, including video courses (but not free).