I am always interested in reading books that have a connection to my family. I recently found a book entitled, "Tierck Clafsen DeWitt and Descendants of His Son Luycas DeWitt," written by Vona DeWitt Smith. The book was published in 2004 in Victoria, Canada
I was so disappointed in the book as I found many errors in this book. The first error that I noted was in the title of the book. The author apparently does not know about the short or descending s. Clafsen should read Classen. Clas is a diminutive of the name Nicolaes and is often written as Claes. Tjerck/Tierck was the son of Nicolaes (Claes).
I found several errors in the locations of events, such as, Clinton, MI when the location was actually in Clinton, IL. I also found errors in dates. Birth, death and marriage registers, social security death index, draft registration and census records often conflicted with the dates presented in this book. And in some cases, the given name or surname in the book could not be found in an Internet search or in a search at many of the genealogical services to which I subscribe. However, I did find hits when I made some simple modifications to the spelling like changing the letter u to the letter a or adding a consonant.
Some of the errors should have been caught by proofreader. When a child's birthdate is within a few years of the birthdate of the parents, a proofreader would have caught that.
The book is available on Amazon but I would caution you to take whatever information is provided with a grain of salt and look for other records and documents to support your findings.