Yes, you could say that once you've got the main idea, then you might as well just abandoned the book.

是的，你可以说一旦你有了主旨，那么你还不如放弃这本书。

It was obvious to his more logical mind that the secrecy to which they had bound themselves must be kept in its fulness, or might as well be abandoned altogether.

对他比较合乎逻辑的头脑来说，很明显，他们必须完全保密，否则还不如完全放弃。