The Incredible Mr. Black — Rachel E. Rice

When Maximilian Blackstone, who is into bondage and S&M, meets a young woman named Alexander, he instantly falls in love with her. However, on the first night she sleeps with him, and then she discovers his secrets, which includes a twin brother who is more damaged than him. Alex, as Max calls her, has a few secrets of her own.

Alex matches wits with Max to change him, but she soon falls under his spell, and is willing to do anything for him except for one thing. Is she willing to step into his world of bondage and S&M without losing herself? 

This book contains a secret baby, bondage, ropes, and plenty of secrets.