First I want to say Thank You for your blessing.
Granth Sahib does not translate very well into English. Granth means Book or Scripture. Sahib means Lord or Master. The entire name is Sri Guru Granth Sahib which means Sri (Shining, radiant, excellent) Guru (Teacher, light, dispeller of darkness) Granth (Book) Sahib (Lord, Master or even Friend). Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/interfaith-dialogues/23539-creator-is-self-created.htmlReference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=23539 Put it all together: Radiant Teacher Sciripture Lord and Master.
Translation: Sri Guru Granth Sahib is The Radiant Teacher, The Light Who is Our Scripture, Lord, Master and Friend.
There is something of a problem recommending books that explain the Guru Granth Sahib. Built into Sikh faith is this idea: we are all learners and that Guru Granth Sahib is the Teacher and the Book. Thus, many Sikhs well-educated in gurmat vichaar, understanding the guru's wisdom, are reluctant to say that they are "teachers." We do not have clergy who would be "official" experts. Sikhs argue a lot and distrust experts. I refer you to this link as a starting point. This is the one I use over and over again. Here it is Sikhism: Reflections On Gurbani
There are some very good essays here at SPN written by forum members in fact. Over the days and weeks other members will add to the list I am sure. I will add to the list.