Alice Adams’s irresistible debut novel falls squarely into that most ­English of genres: the comedy of manners ... A crackerjack storyteller who deeply inhabits her characters — deploying pitch-­perfect dialogue to poignant and hilarious effect — Adams uses the conventions of the form to examine larger ideas about class and commerce, art and science, friendship and family at the time of the most recent fin de siècle ... Ultimately, though, this is a novel that strives to define a generation — the one known, ominously, as X — and it falters when Adams overreaches, struggling to establish her characters as representatives of their era, shaped by the historical events of their day.

...[a] bittersweet and compassionate novel ... The friends’ fates rise and fall. There are career highs and implosions, marriage and infidelity, addiction, prison — and funny, biting insights on how relationships can detonate when one friend has children and another does not ... it’s in Sylvie’s hard fall that the beauty and depth of the book resides.

Ms. Adams has managed to combine a hoary premise, a familiar plot, readable to iffy prose and pigeonhole-ready characters and spin their story into a heart tugger with seemingly honest appeal. This amazing feat doesn’t rival those of the Large Hadron Collider, which plays a cameo role in Invincible Summer. But it’s close ... Invincible Summer, which takes its title from an uncharacteristically upbeat Camus quotation, means to focus on bigger, less fluffy things: moving from a sheltered academic life to an unprotected one, facing increasingly consequential problems, making serious decisions and, inevitably, serious mistakes. It also takes some notice of the world around its self-involved foursome ... Ms. Adams captures the way that freedom begins to erode as each character defines himself or herself more clearly. As the lines that separate them are drawn, the friendships become more competitive and awkward ... Ms. Adams’s story develops an increasing power that can be created only incrementally. And by the novel’s end, regardless of whether you buy the plot’s string of remarkable coincidences, its message of friendship, love and loyalty hits home.