Just read through the entire Biography of both the generals so i will give you a really short summary:
Bai Qi:
-Mainly about which war he participated in during his military career, with most focus placed in the Battle of Chang Ping(im sure wikipedia has the information on this battle).
-The last part of Bai Qi's biography writes about how he denied King Zhao's order to take command of the Qin army during the Seige of Han Dan, and died a tragic death by committing suicide(details here).
Wang Jian:
-Similar to Bai Qi, the first part was dedicated to recording the various wars Wang Jian participated in.
-The next part writes about the war with Chu involving both Wang Jian and Li XIn in detail, which im sure you probably already know about.
-There are also a few mentions about his son, Wang Ben, and the states he destroyed, mainly to show that it was the Wang family who united China for Qin.
-The last part was about the time just before the fall of the Qin dynasty a few decades later, after the Meng family were killed by Zhao Gao and both Wang Jian and Wang Ben were dead(presumebly due to old age). Wang Li, the third generation of the Wang family, was then tasked to carry the name of the Wang family to defend Qin from army of Xiang Yu, which he failed and was captured.
The last part of the entire chapter is a short comment written by the author Sima Qian himself(he does that for every chapter). He commented that Bai Qi might be the best general in the entire China then but he was defeated by his own master. Wang Jian might be the general who helped his king conquered the entire China, but he was unable to help his king rule his land with morality, leading to the downfall of Qin and his own grandson being captured by the enemy. In conclusion, even the best generals have their weaknesses.