Robert Sadleir's bio of the Lyttons, Bulwer and His Wife: A Panorama, 1803-1836, is just as biased* and speculative as the rest. Sadleir has even less excuse than other biographers, though, as he had less of a personal connection and more scholarly experience than the family members and friends who had written about the Lyttons previously. His work is worth mentioning because he manages to introduce a somewhat novel element into the story: he claims that Lady Caroline Lamb orchestrated the whole relationship. She pushed them together, and and she set them up to fail. Gosh, now it all becomes clear! It's not Edward and Rosina's fault that their marriage failed; it's Lady Caroline Lamb's fault! Caroline Lamb has appeared in other versions of the story, including the Louisa Devey and Victor Lytton efforts, but by no other biographer has she been accused of such a dastardly deed.
Sadleir's work is available in the stacks as well as in Special Collections, and I am dismayed to find it catalogued as "nonfiction."
*Pop quiz: based on the title, can you guess which of the Lyttons Sadleir favors?