I have French A1, Spanish B1/B2 and English C1 levels, while being a German native speaker. It will be hard for me to really comprehend Spanish written books that are not written specifically for teaching language. In English I can read more difficult non-fiction, but I need to look up some terms every few pages. Hell, even me being a native German speaker does not mean I understand every German book.

with understanding not only the contents written but infer on the novels concepts and relay reading comprehension akin to a native speaker

C1/C2, leaning more towards C2.