The Rosie Effect by Graeme Simsion

With The Rosie Project, "Graeme Simsion achieved the impossible and created an entirely new kind of romantic hero," Jojo Moyes, author of Me Before You said. Now Don Tillman returns in the hilarious and charming sequel to the international sensation. Get ready to fall in love all over again.
Don sets about learning the protocols of becoming a father, but his unusual research style gets him into trouble with the law. Fortunately his best friend Gene is on hand to offer advice: he's left Claudia and moved in with Don and Rosie.

Picking up where The Rosie Project left off, The Rosie Effect is a fun, hilarious, and poignant read. "Don Tillman helps us believe in possibility, makes us proud to be human beings, and the bonus is this: he keeps us laughing like hell" (Matthew Quick, author of The Silver Linings Playbook).