The Observer review has a footnoted reference to John Sutherland's forthcoming Curiosities of Literature: A Book-lover's Anthology of Literary Erudition (Random House Books, ISBN: 190521197X). From the publisher's blurb:
How much heavier was Thackeray's brain than Walt Whitman's?* Which novels do American soldiers read?** When did cigarettes start making an appearance in English literature?*** And, while we're about it, who wrote the first Western,**** is there any link between asthma and literary genius, and what really happened on Dorothea's wedding night in Middlemarch? *****
Without diminishing the value of John Sutherland's more scholarly works (see his bibliography), for me this looks a welcome return to the discursive, eclectic and immensely readable books - Is Heathcliff a Murderer?: Puzzles in nineteenth-century literature and so on - that first brought his work to popular readership (see the previous A Nasty Case Of The Vapours).
* 376 grammes, if we're to believe Dissecting the brains of 100 famous men for science; "The Actual Weight and Tissue of the Brain Are Significantly Correlated with Mental Superiority, Says Dr. E.A. Spitzka --- The Twelve Biggest Brains in the World". (New York Times, September 29, 1912)
** Heinlein's Starship Troopers is on some lists, though not on this fairly standard US Army Combined Arms Center and Fort Leavenworth list where it's quite surprising to find Catch-22.
*** Around 1850? A number of people are smoking them in Dickens' 1857 Little Dorrit (EText-No. 963, Project Gutenberg); the concordance (p925, Penguin Classics edition, 2003) notes, interestingly, that the occurrence is anachronistic for the book's 1820s setting, since they didn't catch on until popularised by soldiers coming back from the Crimea with the habit. This isn't the only time Dickens makes such a mistake; Sutherland's earlier Can Jane Eyre be Happy? wonders why Magwitch in Great Expectations is sentenced to death for coming back to England a decade or two after the death penalty for returning transportees had stopped being enacted.
**** The classic answer is Owen Wister's 1902 The Virginian, a Horseman of the Plains, but Googling finds other contenders such as the many dime novels of Prentiss Ingraham including the 1887 Buck Taylor, King of the Cowboys; or the 1878 Live Boys, or Charley and Nasho in Texas (an account of a trail drive by Arthur Morecamp - a pseudonym for the Texas attorney Thomas Pilgrim); or even various 1860s chapbooks such as William H Bushnell's 1864 The Texan Herdsman: Or, The Hermit of the Colorado Hills. A Story of the Texan Pampas.
***** A long-running topic in academic analysis of the causes of Dorothea Brooke's rapid disaffection with her marriage to the elderly scholar the Reverend Edward Casaubon.