That book is, in my estimation, a necessary primer for those not versed in the history of Islam's interaction with the West. Try copy/paste this one->
http://www.newenglishreview.org/Emmet_Scott/Mohammed_%26_Charlemagne_Revisited%3A_The_Epilogue/
The Epilogue gives one an excellent taste of the book.
One could, of course to go to Henri Pirenne, himself, whose thesis occasioned Scott's book but Scott updates and adds information that was not available yet to Pirenne.