What should my book be about?

How long is the average novel should to be? Cause i've already got 30 pages written. I'm currently writing a book where the main character is a 42 year old divorced mom of 6 who is constantly thinks she's still 20. she's secretly still in love with her ex husband who is engaged to a golddigger...plus her teen daughter is dealing with a unplanned pregnancy. What would be the best title for my book? Oh and i'm planning to give my book a jackie collins/harold robbins feel to it...how would the public respond to that cause i'm 17. What should i add to the book? Cause i was thinking of adding like a "secret diary of a call girl" plot twist to it? Any suggestions are welcome. Thanks and xoxo