Reddit mentions of Samuel Johnson's Dictionary

as a kid, i used to grab the dictionary whenever i got bored. mom bought a set of the World Book Encyclopedia, and with it was a two-volume dictionary. i had no idea most people would think it was odd, or i'd have probably stopped reading it. but frankly, it was great fun. i'd learn a bunch from just a single page.

arguably, though, Johnson's dictionary is probably the most "readable" in terms of straightforward enjoyment and entertainment. of course some usages are now antiquated... but you might find it a good option if your desire is to read from A to Z, literally, in order.

"He is even believed to have made up some words. His definition of oats is very rude to the Scots. He defines the word as 'A Grain, which in England is generally given to horses, but in Scotland supports the people.' Johnson was criticised for imposing his personality on to the book. However, his dictionary was enormously popular and highly respected for its epic sense of scholarship." From the British LIbrary. You can get an abridged reprint HERE

The OED is the grand poobah. but a full set is not viable, unless you want to read it in the library. The condensed two-volume set requires a magnifying glass.... But if you wanted as close an experience to the real thing, an abridged Oxford English Dictionary would be excellent. I like the OED because it delves into etymology, and the usage examples are the definitive examples of first known appearance in print.