Lewis Lin has a lot of great stuff, too! Cracking the PM Interview was definitely the first book I bought. I feel like Lewis Lin’s book reviews tougher questions though.
OP try giving this text a read: https://www.amazon.com/gp/product/0615930417/ref=as_li_qf_sp_asin_il_tl_nodl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0615930417&linkCode=as2&tag=seatintecoac-20
Basically a CC functions like this: Credit card companies make the bulk of their money from three things: interest, fees charged to cardholders, and transaction fees paid by businesses that accept credit cards.
Think of a credit card as a short term loan, so if you were to start lending money, what would you look into first? Determining who your target market is. Is the CC for college students, first time creditors, arm forces members, state employees, mid income or new creditors with 0 credit?
How are you finding your CC company? Will you have crediting investors who would get profits from the collected interests over time it will you have shared holders of a financial institution?
Think about how you would go about establishing credit worthiness, credit interest tiers, payment methods, insurance, security and fraud etc.
Hope this gives you something to start on.
As others mentioned, there's a ton of great new content coming out recently, out of both Mind the Product and Product School.
Check out the classic Decode and Conquer by Lewis C Lin: https://www.amazon.com/Decode-Conquer-Answers-Management-Interviews/dp/0615930417
Also there are some awesome new YouTubers putting out PM content, like Garrett Rysko: https://www.youtube.com/watch?v=Tpsmlr_8cyA