For something to “sell” (or “go off”) “like hotcakes” (or “like hot cakes”) is for that thing to sell very quickly—a great success. The expression has been popular in business.
   
“These (books—ed.) sell like hot cakes in this region, I suppose?” was published in the Cleveland (OH) Whig on February 24, 1836. Hot cakes were popular food items in the 1830s.
 
   
Wiktionary: sell like hot cakes
Verb
sell like hot cakes
1. (intransitive, idiomatic) To sell quickly.
   
(Oxford English Dictionary)
hot cake, n.
colloq. In pl. in like hot cakes, as the type of something very desirable or in great demand; orig. and frequently in to to sell (also go, go off) like hot cakes.
1839   C. F. Briggs Adventures Harry Franco I. xi. 74   ‘You had better buy ‘em, Colonel,’ said Mr. Lummucks, ‘they will sell like hot cakes.’
1879   Congress. Rec. 15 May 1368/1   Four per cent bonds..go off like hot cakes.
1908   Daily Chron. 4 Aug. 3/4   Ice creams at 3d. a time went ‘like hot cakes’.
 
24 February 1836, Cleveland (OH) Whig, pg. 2, col. 5:
While in a book-store in Albany, a few days since, we noticed a large number of Holland’s Life of Van Buren lying up on the counter. ‘These sell like hot cakes in this region, I suppose?’ we observed to the bookseller. (...)—Bath Const.
 
July 1839, The Knickerbocker; or New York Monthly Magazine (New York, NY), pg. 79:
THE ADVENTURES OF HARRY FRANCO. A Tale of the Great Panic. In two volumes. pp. 525. New-York: F. SAUNDERS.
Pg. 80:
“You had better buy ‘em, Colonel,” said Lummucks; “they will sell like hot cakes.”
 
Chronicling America
16 July 1839, Morning Herald (New York, NY), pg. 1, col. 1:
NEW YORK, June 29th, 1839.
(...)
... you had better send soon as they will all be gone for they go like hot cakes and then there will be no more of them.
Yours Resp
M. H. C.
 
NYS Historic Newspapers
17 July 1839, The Evening Post (New York, NY), pg. 2, col. 3:
NEW YORK, June 29th, 1839.
(...)
You had better send soon, as they will all be gone, for they go like hot cakes, and then there will be no more of them.
Yours Resply,
M. H. C.
     
OCLC WorldCat record
GAZETTE GOING OFF LIKE HOT CAKES! —We have been quite
Publisher: VINCENNES, INDIANA
Edition/Format: Article Article
Publication: VINCENNES GAZETTE, (January 25, 1862)
Database: The Civil War: 1855-1869
 
OCLC WorldCat record
SMAL/80 This new microcomputer language is great. So why isn’t it selling like hotcakes?
Author: Willis J Tompkins Affiliation: Department of Electrical and Computer Engineering, University of Wisconsin-Madison
Edition/Format: Article Article
Publication: IEEE Engineering in Medicine and Biology Magazine, v3 n1 (198403): 34-35
Database: IEEE Publications Database
     
OCLC WorldCat record
Selling like hot cakes : and other poems
Author: N Cookson
Publisher: Eden, N.S.W. : Anthony’s Desktop Pub., [1996]
Edition/Format:   Print book : English
 
OCLC WorldCat record
Cooking titles sell like hotcakes: First-half circulation figures are in, and food and money magazines are leading the newsstand charge
Edition/Format: Article Article : English
Publication: FOLIO -NEW CANAAN THEN STAMFORD- 25, no. 13, (September 15, 1996): 24-25
Database: British Library Serials
Other Databases: ArticleFirst