I read a lot of Arthurian material. Malory, de Troyes, stuff from many other writers over centuries translated from Welsh, French and German and... If you really want to have half a handle on Arthur you need a good survey book. My favorite is https://www.amazon.com/Development-Arthurian-Romance-Sherman-1887-1966/dp/1013415752/ref=sr_1_1?crid=IIXYPLON65D7&dib=eyJ2IjoiMSJ9.kQ_Ar0TJ6oldOB1OWCA5wNfsYsryURW8qzXnEKVeFhUyWD5e6TAcMOPuyUP_7YxuQLv3LpoWJPUN7jiNJzIogQ.x802ORl7UiaHEhQUpCIy1iu_2Wb4_Z6mse3PfVBbuNE&dib_tag=se&keywords=The+Development+of+Arthurian+Romance+Loomis&qid=1781645765&s=books&sprefix=the+development+of+arthurian+romance+loomis%2Cstripbooks%2C220&sr=1-1 - My second favorite is https://www.amazon.com/Arthur-King-Britain-History-Chronicle/dp/0390121606/ref=sr_1_3?crid=106IWW6SZRA9E&dib=eyJ2IjoiMSJ9.U5A_rgo84XQnIbuNN6WBVfk6u4rV8Lsnqty9rcHd3FOYqfRXMk8fft3veVFPO1NPmR3rOc7Lv33XxmOwVn2uIPcIOYZunWChppCoqu4fWyiC8LZo2VqI_DRqvwGfzk81QP2gllLJwZv3f5qEZtT0ik7zLXRIJ1oy6GlgaJXwseQAk7K-1eLVXt8IUTK8uzVxaZPNCoLHsU4SCOhrcwnDCv36x9NgZqEGxRAVC9o17kI.8LXJM6WuOhiMYt4BYLZs-l_vExiDSzTszfsOz0wu0O0&dib_tag=se&keywords=Arthur+King+of+Britain&qid=1781645832&s=books&sprefix=arthur+king+of+britain%2Cstripbooks%2C323&sr=1-3 - In these you get the origins, development and you find that Malory was a latecomer who put a lot of earlier material together, made up some new stuff and whipped it into the shape we now think of as King Arthur.

