For the most part, I have found the information for the descendants of Aaron Asbell, Ridge Spring/Monetta, SC in the George Bennett book and the Asbill/Asbell Connections book to be reasonably accurate and independantly verifiable through census records, cemetaries, oral history, etc. That being said, I have found some errors and have not verified (and don't plan to)every SC Aaron Asbell descendant listed.
I expect we owe this accuracy to Miss Belle Williams, Monetta, SC, who captured and forwarded the information to Mr. Bennett and to the fact that the Edgefield courthouse never burned.
These books are a great starting place for information on SC Asbells after Aaron settled in 1799. I cannot speak to (though I think other posters have adequately pointed out the errors)the information prior to Aaron's arrival in SC, nor to the Asbell's who settled in other states.