Mage's Handbook

Chen Yi unexpectedly transmigrates to a modern society with supernatural powers, but his talent is mediocre, and he seems destined to become one of the ordinary masses, living a mundane life. Just as he is about to accept this fate, he binds with the Mage's Handbook! "An excellent mage should have the pattern of showing off in public, the demeanor of staying low-key, the composure to let villains speak, and the contract spirit of using and discarding..." So says the Mage's Handbook. ... — Description from novelcodex.org