When people ask me why I think Emerson is America's greatest thinker and essayist, I have trouble explaining it. Most people are used to reading Emerson's carefully crafted essays, which scintillate with ideas and lapidary prose. You can pull out lines and paragraphs from almost any of them and think about them for days, finding fractal ideas within them that resonate in your own mind.
But what really convinced me was when I started reading his journals. First, I had read some of the books available that contain excerpts from the journals; there are several, of varying length. Then I bought a set of the 1910 edition, edited by Emerson's son Edward, and started reading them. In ten volumes, with small pages and largish print, they are only slightly better than the one-volume editions of excerpts. Finally, I bought the 16-volume Harvard University Press edition - a massive expense - and am currently reading them (and posting my favorite excerpts on [...]).
Reading Emerson's "private" writings - journals of this period were not diaries, but were often passed around, so Emerson knew that others would eventually read what his contained - showed me the type of thinker he really was. When he writes extemporaneously, his ideas flow more fluidly, less densely than in his essays. While he reused parts of the journal for his sermons, at first, then, later, his essays, there is a spontaneity that one doesn't find in the published works.
So this Library of America edition is a boon for anyone wanting to discover Emerson's journals. I'm a big fan of the LoA books, for their choice of authors, and the quality and readability of the books themselves. These two volumes are my choice for bedside reading, and, while they only include some 1/6 of the full journals, that is more than enough for most people. (With the price of the HUP edition, affordability is another criterion to take into account.)
If you fall under Emerson's charm, these may end up being books that you read over and over, either starting over from the beginning each time you get to the end, or just dipping into them from time to time. Lawrence Rosenwald has made a judicious selection of journal entries, giving these two volumes a feeling of completeness, even if they are but a fraction of the whole.
Those wanting to go further might want to pick up (or borrow from a library), the obscenely expensive Emerson and the Art of the Diary, which looks at Emerson's production of his journals, and looks at journal writing in general. It's a fine handbook to accompany these two volumes. If only OUP would release an affordable paperback edition of the book, more readers of the journals would be likely to buy it.