Define 'better'...

How about 'more accurate' as a measure...

Then every text book is an example of this measure of better improving over time...

How about 'more representative of the human experience'... (or enjoy/like more)

Then we measure how well a human relates to a book: which is taste, a subjective quality that is notoriously hard to measure in any meaningful way. This measure becomes not a single measure, but a collective measure against the sum of humans who interact with it: an untenable standard - and biased towards the present anyway - which doesn't give charity to your position.

...So how do you measure a book to be 'better'? That's the neat part: you don't. You can measure what you 'like' more, you can measure 'features'... but we probably won't even agree on what makes a book 'better'. We like what we like, and most of us have a hard time even explaining why we like something.