So exited to reading!

So excited to be reading! [Alternative: Reading is so Exciting! So Exciting to be Reading!]

The present participle (-ing form) is never preceded by "to". It is either used as if it were a noun, or is preceded by an auxiliary verb, usually a form of "to be".
"So excited to be reading!" is OK in a title, but it is really an abbreviation of the complete sentence "I am so excited to be reading!" "So Exciting to be Reading" is an abbreviation of the sentence "It is so exciting to be reading."

I didn't realize that reading books is/was very interesting until today.

Now I'm half way through the first one of a series of seven books. [Alternatives: "first book in a series of seven", "first in a seven-book series"]

I will read it one more chapter (in it) then go to bed.

I wish I didn't have to work tomorrow.

If I didn't have to go to work tomorrow, I would keep reading until dawn.

In a conditional sentence where the condition is false, use the past tense of the verb in the "if" clause (as you would use the ～たら form in Japanese). "I would keep reading" is perfect.