Sitting with Koans: Essential Writings on Zen Koan Introspection by John Daido Loori explains a lot of the cultural origin and way to approach Koans. This is the best resource I can recommend cause it gives you the proper historical and philosophical framework beyond them just being riddles. For further studies: Chan Insights and Oversights by Bernard Faure more in-depth explains the way Chan/Zen has functioned historically and presently. Additonally: The Letters of Chan Master Dahui Pujue by Jeffrey Broughton This will show you how a Chan Master functioned and percieved himself and differing sects of Zen at the time. A big point of context that is generally lost in the modern day, to grossly simplify, is that the school of Zen that retrospectively can be seen as being very focused on Koans, Linji/Rinzai Zen in modern times is far less dominant thatn the Caodong/Soto Zen school that moreso prioritized meditation without the same focus on Koans and Hua tou. Again thats an extremer simplification, but that context helps you understand the modern state of things pretty well

I genuinely cannot figure out if this is a troll post or serious inquiry, but if the latter, then Shunryu Suzuki's Zen Mind, Beginner's Mind is an excellent text because a central theme is that you do Zazen meditation because you do it, and finding a "rational" grounding is a fool's errand (comment below sums it up pretty well). To put it in a more Western context, the Sam Harrises of the world will point out that the Bible is an illogical, incoherent guide for living, assembled by disparate writers over the course of centuries with their own ideological agendas, which were in turn were compiled by institutions of state power with their own ideological agendas, all of which is true -- and all of which is completely irrelevant to the inspiration that Christians and Jews find therein. You might not know the tempo, the time signature, or the key of the song, but why should that stop you from dancing?

zen koans are not meant to be understood on a baseline language level. they're used to break you out of linguistic logic and to have an experience that can't really be verbalized. (zen) buddhism is about shattering preconceived notions about reality so you can escape samsara. spiritually and philosophically related: the first line of the Tao Te Ching is "The Tao that can be told is not the eternal Tao. The name that can be named is not the eternal name." anything that can be described to you in regular language is not enlightenment and takes you further away from the actual experience. language is distraction. sorry i have no resources tho :(