Learn Linux for free this summer through EdX and Harvard U.

Surge

Its definitely entry-level. I don't have much Linux experience so syntax to a point is new to me but nothing I would call challenging at this stage.. im on ch: 8 myself. Have not had much time to keep going.

I think its not a bad kickstart but any good linux starter book is likely going to dig in deeper faster and be better resource if someone wanted to stick with Linux or go into any certs.