Binchy's final book A Week In Winter was published posthumously following her death at the age of 72 in July.
It makes it a bittersweet Christmas for her many fans, since this is likely to be the last time Maeve will be at Number One.
A Week In Winter is a series of interlinked stories revealing what goes on in a West of Ireland hotel among a group of people on an out-of-season break.
The book is vintage Binchy and is full of humour, sharp dialogue and the keen observations that the former journalist became famous for during her writing career.
At 6,402 copies sold in the past week, it is selling more than twice as fast as the next fiction book in the top 10 chart, Ross O'Carroll-Kelly's The Shelbourne Ultimatum.
Sales so far are double that of her previous novel Minding Frankie.
Second on the chart in the Nielsen Bookscan figures for Ireland, released yesterday, is the latest in the Wimpy Kid series, a huge hit with children around the world. In third place is the annual Guinness World Records, which is a best-seller every year.
Jamie's 15-Minute Meals is this year's must-have cookery book, and is at number four in Ireland -- although it's number one in the UK having finally passed JK Rowling's first adult novel, A Casual Vacancy, last week.
Neither Rachel Allen or Catherine Fulvio, who both have new cookbooks out, have even made the Top 10 here.
The Book Of Irish Mammies rounds out the top five.
One of the big surprises is Calm The Soul, the book of prayer from the Poor Clares in Galway which is at number eight and may be a reflection of the pressure so many people are feeling as the financial cutbacks hit home.
At number nine is the only sports book to make the list, the story of John 'The Bull' Hayes, the ordinary guy who became a rugby legend.
Sneaking in at number 10 is Tolkein's The Hobbit, thanks to publicity from the new film.
It's interesting that so many readers young and old are buying the original story rather than one of the various movie tie-in books that are also out.
The full top 10 is:
1. A Week In Winter -- Maeve Binchy (6,402 sold)
2. Diary Of A Wimpy Kid: The Third Wheel -- Jeff Kinney (5,687)
3. Guinness World Records 2013 (4,424)
4. Jamie's 15-Minute Meals -- Jamie Oliver (3,494)
5. Isn't It Well For Ye?: The Book Of Irish Mammies -- Colm O'Regan (3,126)
6. The Shelbourne Ultimatum -- Ross O'Carroll-Kelly (2,738)
7. Just Mary: My Memoir -- Mary O'Rourke (2,255)
8. Calm The Soul: A Book of Simple Wisdom And Prayer -- Poor Clares, Galway (2,110)
9. The Bull: My Story -- John Hayes (1,736)
10. The Hobbit -- JRR Tolkien (1,708)