"We're just pleased for Richie that his book's so successful.
"Everybody's interested in Richie. It's very hard to find a bad word said about him, and all of us who know Richie know he's a good guy who's an incredibly good sportsman.
"You put that together with a writer of particular skill and you end up with a great book about a great person."
Mr Chapman said he'd contacted international publishers for confirmation of the record. He believed the previous best-selling rugby book was former English captain Martin Johnson's autobiography. It sold 70,000.
Jonah Lomu's Jonah sold 45,000 in New Zealand and 20,000 in Britain.
"Unless there's something that's completely bamboozled us, we think we've got a pretty good idea [about the record]."
He expected McCaw's to follow the pattern of Sir Colin's second book, Meads, published in 2002. It remained in demand for two years after it was launched.
Last night, McCaw was named the Kelvin R. Tremain Memorial Player of the Year at the rugby awards, which also saw accolades for All Blacks coach Steve Hansen and the world-champion All Blacks, who were coach and team of the year respectively.
All Blacks flanker Liam Messam was named the Tom French Memorial Maori Player of the Year, Hurricanes centre Conrad Smith the Super Rugby Player of the Year and Canterbury player Robbie Fruean the ITM Cup Player of the Year.