The Red Book Of Westmarch

[Boromir88]

I wouldn't say it's written badly you just got to look at this one small phrase...

It (The Red book) was in origin Bilbo's private diary,

So by saying "in origin" mean "It" (the red book) was originally Bilbo's diary of his accounts, then became known as the "Red Book." Think of it as Tolkien's letters, and early drafts, then out of those jumbled masses of notes, rewritings, changes, you come up with LOTR, Sil...etc.