Should I continue the book series?

I read the first 12 books of Lone Wolf and I loved them. I'd like to continue the series but there 20 more books (21 if we count both Light of the Kai books that still aren't published), and each book costs around 16€ in my country, so buying all of them would cost 320€ (or 336€). Also my mum said she wouldn't like to continue buying me Lone Wolf's books. But I discovered that there is Project Aon, where I can ready almost all Dever's books free.

Should I continue buying books or are the online version worth it? Which one should I do?