PewDiePie mentioned Don Quijote de la Mancha by Miguel de Cervantes Saavedra 4 times

Everyone knows Don Quijote for its humour and for how silly it is and what a loveable character it is but, and yes it is, it is very humorous, but after reading it I realised that it is so much more than just that. And I'm so glad I read it. It's my favourite piece of classical literature that I have ever read. [...] It's the longest book I've read but it is also the longest book I've ever enjoyed and honestly, I can't wait to reread it. I could go on more, but there is really no point. It is quite hard at some points. I would be lying if I said that it was the easiest read I ever had but it is 100% worth it! Check it out! Don Quijote 5 out of 5. Beautiful, so glad I read it!

— PewDiePie

On Felix's bookshelf.

First off we have 'I am a Cat' by Soseki Natsume. It's a Japanese writer who spent some time in England and then he came back and then he published this in a magazine only I think the first chapter he wasn't planning to make it into this beast that it is today but people liked it so much that he kept publishing it and uh yeah maybe that's how you were supposed to read it just like in parts here and there. [...] This book is a satire, it's a very old satire but that doesn't stop it from being enjoyable, just like Don Quijote or any other book that is well written.

— PewDiePie

Number two - Cervantes' Don Quijote. There is never gonna be a better time in your life than now to read this book, because everyone should read this book at some point in their life and you will be happy that you did it. Do not give up in the middle because it got a little difficult, keep reading.

— PewDiePie