You say she won't talk to you but she has questions about sex. That screams that she needs to get some answers and she needs those answers from you. Wouldn't you prefer to give her the correct answers vs her getting wrong info at school or on the internet? Does she ever talk to you? Do you two have any sort of communication with each other?
I feel it is important to have a no topic off limits line of communication and most of the time... you as mom are listening OR talking WITH her not AT or TO her.
If you feel uncomfortable talking to your daughter about sex and facts of life, then talk when you are walking in the park, driving down the road, etc so you don't have to look at each other. She needs to know it is OK to talk about these things. She's probably hearing things at school and she simply needs confirmation of what is true or not.
I know she is just 10 and at an age where she is changing and yes of course she might feel like she can't talk to mom about things like that. She knows her body will be changing as many of her friends may be going through different phases of puberty.
Just a book is not going to cut it. If you use books along with communication it will be more effective plus help you build your relationship with her. That relationship is in for many changes through the next 8-10 years and right now is what sets that relationship up for the future.
If you already know her questions, you have a start... make a fun date and include communication about sex, boys, the color of the sky... just talk.