I have read Salma Farooqi to get a basic understanding of Medieval Indian History. However, it doesn’t offer much more than that. You can’t expect to take on the optional paper with just Farooqi’s book.
As for Irfan Habib, I have selectively read his Medieval India: The Study of a Civilisation. It is a small book and a light read. Again it doesn’t cover all the portions of the syllabus.
In addition to these two books, I complemented medieval India with two more sources. One was Baliyan’s notes. Even though this too lacked in many aspects and was outdated with regard to some portions, it reinforced the understanding I gained from Salma Farooqi.
The best source to go beyond the political history of India of the early medieval and medieval period are the history textbooks of IGNOU. They cover the socio-economic history in detail.
I would recommend that you refer IGNOU textbooks as your primary source once you have a good understanding of the political history of the period. If you don’t have that, then IGNOU textbooks will be a little bit difficult to follow.
All the Best.