there is so many books ...before???

[ripley]

Hi, I cannot understand why in this sentence it is used there is and not there are; besides I cannot understand the structure of the sentence considered as a whole
There are many books that I can read about a serial killer (????)
before (???) I'm bored.

A woman says:
There is only so many books that I can read about a serial killer before I'm just bored and have had enough.

I understand the overall meaning: there are many thrillers which bore her; but I cannot understand how the sentence is constructed. Please help me understand how the fdifferent parts of the sentence are linked to each other!!!! Rip.

[Marylin]

There is only so many books that I can read about a serial killer before I'm just bored and have had enough.

ONLY SO MANY is a phrase in this case. It means that there is only a handful of books that she can actually read before she has had enough (an unspecified but small amount). In other words, once you've read one...you've read them all: they follow the same pattern, the same gruesome crime scene, the same perpetrators, same victims just different methods of killing, etc. That's why her interest is quickly gone.