Wow! Absolutely fantastic. If you are struggling with mikvah OCD anxiety, I cannot recommend this strongly enough. With a beautiful hashkafic introduction and lot of sources from our mesorah, it makes a persuasive case that you cannot argue with your anxiety and trying to seek reassurance will not lessen your anxiety. You have to live with the fact that perfection is impossible and maybe you are going to do it wrong and maybe your worst fears will be correct. That is totally counter-intuitive, but the more I read, the more convinced I am that this makes sense. It then explains very clearly the CBT methods of Exposure and Response Prevention (ERP) and how to apply them to bedikos, shailas, preparation, and after tevila-thoughts. I read Avigdor Boncheck's work Religious Compulsions and I have been hoping for a more niddah focused work. This is it. It's amazing. It's fabulous. I will recommend it to everyone who comes to me suffering from niddah anxiety.