Mrs. Dalloway and Virginia Woolf

Mrs. Dalloway is a novel that relies heavily, sometimes almost solely on its characters to construct a story.  Woolf has done this intentionally, citing the lack of meaningful, plot-independent characters in other novels, which she believes has caused English novels specifically to lose their value.  The Mezzanine and Mrs. Dalloway are therefore similar in that they are attempts to push the novel further, to something deemed more authentic.

I think both Nicholson Baker and Virginia Woolf encountered quite a bit of difficulty in creating their novels because of their determination to break from their respective archetypes.  Because of this, both writers used aspects of themselves to create authentic characters/narrators.  The Mezzanine is a much less personal novel because of its experimental nature; its purpose was to write a novel with a certain style from an abstract perspective.  Baker needed only to push his writing style a bit over the edge.  

Mrs. Dalloway, on the other hand, forced Woolf to flesh out the emotional and existential depth of her characters, inevitably resulting in a more personal novel.  This is especially true because of Virginia Woolf's struggle with mental illness.
Clarissa spends much of the novel considering questions of life and death and existential purpose.  Septimus is confused and lacks any hope or direction in his life, and eventually sees suicide as his sole option.  In this way, Clarissa could represent the intellectual side (perhaps literally as Woolf suffered from multiple-personality disorder) of Woolf, and Septimus the emotional side.  There are certainly times when Woolf seems to be speaking through Clarissa or the narrator, attacking the psychiatrists in a way that stems from personal experience and pain.  Given the fact that Septimus was later added when Woolf decided she wanted Clarissa to live, it's not too much of a stretch to claim that Woolf allowed a "part" of herself to commit suicide in catharsis for herself and Clarissa.

Mezzanine's Purpose

Despite some initial misgivings, I ended up enjoying the Mezzanine; Nicholson Baker's syntax and use of the "white background" was usually engaging, even when the "plot" itself was not.  I initially read the novel as I believe it was intended: to show the interesting and important aspects of what we think is mundane life in the modern world.  There's certainly a lot of evidence that this is what Baker was going for, and I think most of us started identifying with Howie to a certain extent.
But the more I thought about the Mezzanine, the more I started to think of it as an extreme satire.  Instead of Baker writing about the beauty to be found is 20th century life, he may be arguing that 20th century life has become so devoid of purpose, so alike to machines in an assembly line, that Howie and others are forced to contemplate more or less irrelevant topics, such as the evolution of straws, milk cartons, and light refraction in escalators.
Because of this, Howie loses some of his sanity (it seems too strong of a word, but it moves somewhere in that direction), going on for paragraphs about the rejuvenating properties of alcohol on neurons, and making engaging small talk with a coworker about smoke alarms.  Perhaps the most significant scene in the novel occurs when Howie is confronted with the philosopher who states that one should pursue and contemplate "big ideas" instead of the transient.  Howie has a very strong reaction to this, and instead of defending himself or at least contemplating, he simply rejects it out of hand.  The fact that the reader can or must identify with Howie at this point due to the novel's narration from the 1st and 2nd person perspectives only furthers the argument that we in modern society have lost sight of a destination or purpose.