Standard Deviation by Katherine Heiny

This was such a delightful read - I thoroughly enjoyed it. The beginning really reels you in with humor and pathos and a crazy cast of characters.  Here is what Kirkus says:

In her debut novel, the author of the charming short story collection Single, Carefree, Mellow (2015) matures into new (equally beguiling) terrain, exploring marriage, fidelity, friendship, and parenting.
It’s easy to see why Graham, one-half of the New York City couple at the center of Heiny’s first novel, is enthralled by his wife of 12 years, Audra. While Graham, a medical-venture specialist at a venture capitalist firm, is steady, stable, and fond of “routine and order,” Audra, a freelance graphic designer 15 years his junior, is an unrestrained force of good nature. Audra’s vivacity offers a stark contrast to Graham’s emotionally cool first wife, Elspeth, with whom the couple reconnects. Audra draws all manner of friends and random strangers into her orbit with her chatty sociability and almost unwavering cheer. She cannot make it through a trip to the grocery store without running into a million people she knows (Graham says it’s like shopping with “a visiting dignity”) and bonding big-time with the checkout guy, is constantly inviting people (a woman she barely knows from her book group whose husband has been unfaithful; their building’s afternoon doorman, for a reason Graham cannot recall) to move into their den or eat at their table. Audra is forever on the phone, helping out with PTA activities at the school attended by their 10-year-old son, Matthew, who has Asperger’s and is some kind of origami prodigy, or chatting with her best friend, Lorelei. Like Graham, the reader may be deeply enchanted with, if also somewhat mystified by, Audra. She’s a wonderful character, as are many of those assembled around her, and the series of minor challenges she and Graham face (potential infidelities, possible pregnancy, challenging play dates, and other parental concerns)—she pluckily; he sheepishly—make for reading as delicious as the meals Graham is forever called into service to cook for whomever Audra happens to have invited by that night. To quibble, the episodic, somewhat attenuated plot lacks a degree of urgency and loses a bit of steam midway through, but it regains its footing by the end. And to spend 300-plus pages with Heiny’s wry voice and colorful cast of characters is to love them, truly.
An amusingly engaging take on long-term marriage with a lovably loopy character at its center.