I generally have several going at once, but not usually to 'help' me move on through the more challenging. I do sometimes have books on related topics going. There is no real pattern but usually a broad assortment, and I am lucky enough to be a fast reader so rarely spend over a few days on one, even with several going. I love to re-read books I enjoyed, too.

Currently:
Innocent Traitor, a fictionalized life of Lady Jane Grey
A Short History of Nearly Everything, Bill Bryson
Glory Road, Robert A. Heinlein
Benjamin Franklin
Magical Melons, more stories about the kids in Caddie Woodlawn
Leonardo's Swans, another history-based novel
When a Loose Cannon Flogs a Dead Horse, There's the Devil to Pay, about nautical expressions that made it into everyday speech
The Robe (a favorite from when I was a kid)
Iceland
At Swim-Two-Birds
John Mitchel's Jail Journal
Pocket History of Scotland (for someone with big sturdy pockets!)
Death of the Heart, a weird little psychological novel from 1939 I picked up as a bonus at a used book counter.

No one in my family goes anywhere without books on hand; who knows, you might get stuck in traffic or something.

By the way, I loved Godel, Escher, Back, the Eternal Golden Braid, and think Douglas Hofstadter is fascinating, so I think it interesting that so many here seem to have found it heavy going.

Authors I re-read regularly as relaxation include Dorothy Dunnett, Tony Hillerman, Ellis Peters, Bill Bryson, Robert A. Heinlein.

I did once wind up reading Gravity's Rainbow and Ulysses at the same time. This I do not recommend.