Simple Or Less Simple Question Related To Writing.

[Red]

I am asking you, writers, readers, whatever you are:
What is the best tense to write a book?
Past or Present tense?
I am currently using present, i've written over 70 pages, so i think, i won't be intending to change it just now, but is there something particular between these two, which could make it inferior or superioir compared to each other? So superior that it would be better to write in that tense instead?