At last weekend's Borders Book Festival in Melrose novelist Kate Mosse was having an earnest discussion over a glass of wine about Muriel Spark, and whether she would have called herself a feminist.

The conclusion was that she probably would not, but that since she arranged her life exactly as she needed to, in order to write, she embodied the essence of feminism, namely that a woman can make the same kind of decisions, and lead as focused and non-domestic life, as any man.

It's interesting that even in this so-called age of equality, this sort of question is still asked. If you look at bookshop shelves, and book festival programmes, you would think that women writers have, if anything, the upper hand. Women read more fiction than men, by both sexes, and account for the majority of book festival audiences. While the numbers of women running FTSE-100 businesses remains pitiful, and levels of pay in the workplace continue to keep kitten heels firmly in their place, in "the world of books", as one of Spark's characters liked to call it, women novelists appear to be in the ascendant.

This impression, it seems, is misleading. Indeed, in an attempt to raise the issue of women's voices, in literature and in society, Mosse – founder of the Orange Prize (now the Bailey's Women's Prize for Fiction) – has guest edited a strand of the Edinburgh International Book Festival. Across various sessions, she and fellow writers will look at the changing role of mothers, the state of feminism in the 21st century and the ways in which women are portrayed in fiction.

In her latest book, Things I Don't Want to Know (Nottinghill Editions, £12), novelist Deborah Levy beautifully sums up the problem facing many women writers. "Perhaps when Orwell described sheer egoism as a necessary quality for a writer, he was not thinking about the sheer egoism of a female writer. Even the most arrogant female writer has to work over time to build an ego that is robust enough to get her through January, never mind all the way to December."

She obviously hasn't met a best-selling novelist who turned up at the Edinburgh Book Festival with her own bag-carrier, or the many female writers I have met whose self-assurance and sense of entitlement make Martin Amis and Philip Roth look diffident.

Added to the issue of ego, however, is many women's justified grievance that their books are sidelined and treated as intellectually inferior. Jodi Picoult launched a rocket on this subject some years ago, railing against how much more seriously male novelists were taken. In part, the problem begins with publishers who slap pink covers on women's books, no matter the content. As American novelist Meg Wolitzer complains: "These covers might as well have a hex sign slapped on them, along with the words: 'Stay away, men! Go read Cormac McCarthy instead!'"

I despair at the number of women's novels that arrive jacketed in pastels with high heels, handbags and daisy chains adorning the cover, as if women will only be tempted into making a purchase if the book looks like a fascinator or a printed cupcake. Publishing has never been so keen to pigeonhole its authors, and for some women those berths are becoming as tight as Calvin Klein drainpipes.

It would also seem that despite a small army of confident literary sisters, what's true for women in general holds for writers. Even now, most girls are not brought up to be pushy or to feel they are as capable, when it comes to the workplace, as boys. While their male colleagues think nothing of asking for a pay rise, for instance, women often cringe at the thought of appearing to look arrogant.

I'm afraid I have no comfort to offer except to suggest that, given the temperament of most writers, the male writer is probably every bit as insecure as the female. But surely being self-deprecating, or not very confident, or even feeling downright inadequate, is a better asset for a good writer than cast-iron self-belief and a skin tougher than tungsten.