Saheeh Bukhari is the most authentic book, it is at the top of the sihah sittah (the 6 authentics).
Well, obviously we can't just accept every hadeeth we are given.
The ummah has accepted and considered sihah sittah as the 6 most authentic books becuase their compliers had laid down certain clear principles and they contain mostly sound and authentic ahadeeth. Their authenticity has been carefully checked and verified by the ulamaa and muhadditheen(scholars of hadeeth) as authentic.
These are taken into account when testing a hadeeth to be strong:
Rawee-Narrator of Hadeeth
Sanad-Chain of narrators
To be concluded...It seems to be time for bed.