Plenty of room for improvement. At least he's trying and can work on his weaknesses.

A mothers love

The fact that it's drivel is the most alarming bit. How do you put a positive spin on that?

Point them out, he's looking for constructive criticism. Maybe even enrol him into some basic creative writing classes and give him material to read, good solid classics to start with I say 'Old Sport'.

Tell him to take it somewhere to get grammatically fixed, say it in a kind, proud father type of way and I'm pretty sure you won't hurt his feelings OP!

Congrats on the promotion to Chief Editor

I hope he wrote it on Word, usually it's nice enough to show you if your English skills suck.

And that is why we have editors before things are published! Just be honest with him when you give feedback so he can improve it :)

It's nice to see that he was so committed to writing.

Wow, so your teenage son's first book isn't as good as an author who's been writing for years and you're complaining? Teach him better grammar if his grammar is bad. He is obviously motivated and you should be proud of him, and also proud of yourself for raising a kid who has such motivation rather than a kid who does nothing but play video games and smoke weed all day. I understand if it's hard to read, and you of course want to tell him it's great, and it's not, but it's his first try. I wouldn't say f my life over something like that, I'd be happy, and you should appreciate that he's aspiring to do something like this.