While I tend to buy a lot of books, these three were given to me as gifts, which might add to the meaning (that) I attach to them.
I attach to them为定语从句修饰the meaning,省略了作宾语的关系代词that。
《高考英语备考1号·速效编》
《高考英语备考1号·写作编》
《高中英语晨读晚记》
《高中英语错题笔记》
《零起点考大学英语》