Iris Smyles’s new book is a hybrid work, a mix of autobiographical fiction and humor writing that builds a witty, of-a-certain-moment novel. With an unpredictable blend of the confessional and the satirical, the absurdist and the heartfelt, Ms. Smyles chronicles the ins and outs and overnights of a 21st-century single writer-about-town who dwells in the country of her 30s, between youth and midlife.