Reddit reviews A History of the English Language (6th Edition)

He wants to be a linguist--I think he would also enjoy the etymologies in the Oxford English Dictionary. I suggest taking him to a public library and sitting him down with a copy of the OED and going through a few definitions (penetrate would be a good start).

You've definitely got a linguist on your hands--if he also gets interested in computers and/or programming, he will have a lot of jobs waiting for him after he gets through college.

Please PM me if you want more help/advice.

Edit: He might enjoy these books:

http://www.amazon.com/History-English-Language-6th-Edition/dp/0205229395/ref=sr_1_2?ie=UTF8&qid=1377654532&sr=8-2&keywords=english+a+history

http://www.amazon.com/Linguistics-A-Very-Short-Introduction/dp/0192801481/ref=sr_1_1?ie=UTF8&qid=1377654559&sr=8-1&keywords=very+brief+introduction+linguistics

http://www.amazon.com/Professor-Madman-Insanity-English-Dictionary/dp/0060839783/ref=sr_1_1?s=books&ie=UTF8&qid=1377654605&sr=1-1&keywords=the+madman+and+the+professor

I'm reading Baugh & Cable's A History of the English Language 6th ed. and I'm really impressed with how well written the textbook is as well as how much I've learned in the first five chapters alone!

You are beginning with assumptions (unstated assumptions) that are flawed. You assume that language is "correct" or "incorrect" and that is that, but this is patently false. I'd suggest you get this book next time you're at the library: http://www.amazon.com/History-English-Language-6th-Edition/dp/0205229395

I hope you're enjoying the way texting is changing language, because it's only a matter of decades before much of text speak enters standard english. You will sit around and protest, just as a bunch of dead people who don't matter anymore protested every change over the last 1000+ years that made English what it is today (and thereby who shaped what you consider "correct").