I read Rogersons book and I found most of it mixed up and some things are delierbrate errors. Really the writer does not know arabic and has made some stories up. I know I check some of them out but the greatest mistake of this book is that he does not source what he says down. Almost nothing is sourced because of this he could write what he wants and in some cases he did.
He would chop up other stories and want to plant doudt in their heart of the reader. Personally I would not read it again.
i would recommend people to read Martin lings book Muhammad : based on his earliest sources.
This is one of the best in the english language and i would recommend to anyone the writer is Muslim.
I would like to say that many non Muslims write a lot of rubbish about Islam so it better not to read their books. Unless you can break down their ideas which most people can't if that is you then don't read books about Islam by non Muslims they will cause your more harm than good.