To me it is appropriate to mention that you should read A short History of Islam and Muslim rule in Spain by Mazher Ul Haq for both papers. These two books will give you a detailed insight of knowledge as it has accounted every subject at micro level. After reading it, you should also study a brief and upto the mark book written by P. k. Hitti.
These books are trumendously helpful for CSS because Mazher Ul haq book will give you the detailed narration of every subject thus make you at home in solving MCQs and enable you to solve such questions which are a little trickey. On the other hand, P. K. Hitti will give you an intellectual touch thus making you abreast with intellectual knowledge. You should also prepare your own notes after reading these two books which will provide you as "ONE WINDOW" source.
Regards