In addition to the errors that Rusty pointed out...
- "
Pero de repente su vida está cambiando a un ritmo vertiginoso" => This sentence may be 100% grammatically correct but at least in castillian Spanish it sounds really weird. Instead you could write: "Pero de repente su vida empieza a cambiar a un ritmo vertiginoso". If you still want to use the gerund then you could say: "Pero al poco tiempo [se da cuenta de que] su vida está cambiando a un ritmo vertiginoso".
- "
Yo querría leer un libro más excitante" => Same case as above, everything is 100% OK but... if you ask me, it sounds as if you'd rather prefer to read a porn magazine or something
I would avoid the word "excitante": "Me gustaría leer un libro más emocionante/entretenido"
- "el libro
es muy bien para aprender y practicar
[el] español"
Hope it helps!