Fifty Shades is a series of erotic novels by British author E. L. James, initially a trilogy consisting of Fifty Shades of Grey (2011), Fifty Shades Darker (2012) and Fifty Shades Freed (2012). The series traces the deepening relationship between college graduate Anastasia Steele and young businessman Christian Grey. Christian introduces Ana to the world of BDSM.

James has spoken of her shock at the success of the book: "The explosion of interest has taken me completely by surprise." She has described the Fifty Shades trilogy as "my midlife crisis, writ large. All my fantasies in there, and that's it." She did not start to write until January 2009, as she revealed while still active on FanFiction.Net: "I started writing in January 2009 after I finished reading the Twilight saga, and I haven't stopped since. I discovered Fan Fiction in August 2009. Since then I have written two fics and plan on doing at least one more. After that ... who knows?" In August 2013, sales of the trilogy saw James top the Forbes' list of the highest-earning authors with earnings of $95 million, which included $5 million for the film rights to Fifty Shades of Grey. In spite of the success, the books have also been largely panned by critics, with the first entry in particular "being ridiculed by virtually every critic who has read it."

Since 2015 the series has been expanded with a parallel set of novels "as told by Christian": Grey follows the events of Fifty Shades of Grey but from the perspective of Christian Grey, Darker (2017) and Freed (2021) do the same for Fifty Shades Darker and Fifty Shades Freed, respectively.

Salman Rushdie said about the book: "I've never read anything so badly written that got published. It made Twilight look like War and Peace." Maureen Dowd described the book in The New York Times as being written "like a Brontë devoid of talent", and said it was "dull and poorly written". Jesse Kornbluth of The Huffington Post said: "As a reading experience, Fifty Shades ... is a sad joke, puny of plot".

Princeton professor April Alliston wrote, "Though no literary masterpiece, Fifty Shades is more than parasitic fan fiction based on the recent Twilight vampire series." Entertainment Weekly writer Lisa Schwarzbaum gave the book a "B+" rating and praised it for being "in a class by itself". British author Jenny Colgan in The Guardian wrote "It is jolly, eminently readable and as sweet and safe as BDSM (bondage, discipline, sadism and masochism) erotica can be without contravening the trade descriptions act" and also praised the book for being "more enjoyable" than other "literary erotic books". However, The Telegraph criticized the book as "treacly cliché" but also wrote that the sexual politics in Fifty Shades of Grey will have female readers "discussing it for years to come". A reviewer for the Ledger-Enquirer described the book as guilty fun and escapism, but that it "also touches on one aspect of female existence [female submission]. And acknowledging that fact – maybe even appreciating it – shouldn't be a cause for guilt." The New Zealand Herald stated that the book "will win no prizes for its prose" and that "there are some exceedingly awful descriptions", but it was also an easy read; "(If you only) can suspend your disbelief and your desire to – if you'll pardon the expression – slap the heroine for having so little self respect, you might enjoy it."

The Columbus Dispatch stated that, "Despite the clunky prose, James does cause one to turn the page." Metro News Canada wrote that "suffering through 500 pages of this heroine's inner dialogue was torturous, and not in the intended, sexy kind of way". Jessica Reaves, of the Chicago Tribune, wrote that the "book's source material isn't great literature", noting that the novel is "sprinkled liberally and repeatedly with asinine phrases", and described it as "depressing". The book garnered some accolades. In December 2012, it won both "Popular Fiction" and "Book of the Year" categories in the UK National Book Awards. In that same month, Publishers Weekly named E. L. James the 'Publishing Person of the Year', causing an "outcry from the literary world". For example, "What was Publishers Weekly thinking?" asked Los Angeles Times writer Carolyn Kellogg, while a New York Daily News headline read, "Civilization ends: E.L. James named Publishers Weekly's 'Person of the Year'."

The Fifty Shades trilogy has also attracted criticism due to its depictions of BDSM, with Katie Roiphe of Newsweek asking "But why, for women especially, would free will be a burden? ... It may be that power is not always that comfortable, even for those of us who grew up in it; it may be that equality is something we want only sometimes and in some places and in some arenas; it may be that power and all of its imperatives can be boring." Zap2it's Andrea Reiher expressed frustration at Roiphe's depiction of the series, stating that "[b]eing submissive sexually is not tantamount to being the victim of abuse" or that they're "giving up their power or their equality with their partner". Other sites such as Jezebel have responded to the article, with Jezebel listing reasons for Fifty Shades of Grey's popularity, stating that "the vast majority of fans fawn over the emotional relationship Anastasia and Christian have, not about the sex."

In an interview with Salon, several dominatrices have responded that while submission can be an escape from daily stresses, they also frequently have male clients and that trust is a big factor in dominant/submissive relationships. One interviewed former dominatrix and author, Melissa Febos, stated that even if the book's popularity was a result of women's "current anxieties about equality" that it "doesn't mean that it's 'evidence of unhappiness, or an invalidation of feminism,' ...it might actually be a sign of progress that millions of women are so hungrily pursuing sexual fantasies independent of men." Writing in The Huffington Post, critic Soraya Chemaly argued that interest in the series was not a trend, but squarely within the tradition and success of the romance category which is driven by tales of virgins, damaged men and submission/dominance themes. Instead, she wrote, the books are notable not for transgressive sex but for how women are using technology to subvert gendered shame by exploring explicit sexual content privately using e-readers. Instead of submission fantasies representing a post-feminist discomfort with power and free will, women's open consumption, sharing and discussion of sexual content is a feminist success.