如果想说这是我的书,通常说
This is my book 或 This book is mine.
如果想说这是一本关于我的书,则说
This is a book about me.
a book of mine 其实是正确的表达,但是一般都作为主语在句子开头出现,而不说this is a book of mine.
如：A book of mine was made into a movie.我有本书被拍成了电影.