I may be able to provide a brief answer:

John Adams' chief fear was that the proceeding generations of Americans would unjustly and inaccurately glorify the wrong bits of the revolution. He was afraid that students of history would marvel at the military accomplishments of George Washington and company, but forget the decade of political struggle that preceded the creation of the Continental Army.

On a personal note, J. Adams was terrified that his contribution to the revolution against Great Britain, and the subsequent creation of the Republic, would be, in his opinion, unfairly overshadowed by the contributions of men like George Washington or Thomas Jefferson. I think that many people would agree that such a thing has, unfortunately, happened. In the history books, there is a lot of discussion around the drafting of the Declaration of Independence and the Valley Forges and the Constitutional Conventions, but comparably little on J. Adams' trips to Europe in search of funding for the Colonial Authorities or his contributions to the Continental Congress or his handling of the Vice Presidency.

Forgive me for not having my sources on hand - I'm in the middle of moving back to the United States from South Korea. If the mods decide that I haven't provided an adequate argument, they are welcome to remove this post.

John Adams was afraid in his later years that the American Revolution would be misunderstood and truncated by later generations. I would argue that for Middle, High School, and some College students, his fear was realized. Much of what students are taught revolves around a few dates and names, with Jefferson and Washington getting the bulk of the airtime. However, professional historians regained much of the American Revolution through analysis of political cultural materials, writings, colonial government data, economic data, and other key sources. Most university courses on the American Revolution start before the Seven Years War and follow a long trail to the eventual war and its conclusion, even going beyond the Articles of Confederation to the formation of the Constitution. As for historians disagreeing on pieces of the Revolution narrative, there are always dissenting opinions about motivations, importance of certain moments and persons, and attempts to revise the narrative (See: A People's History by Howard Zinn). But largely, there is a modern consensus around the revolution that is best exemplified by Joanne Freeman's Yale Lectures on the subject, which I will link below. In closing, let me leave you with a few quotes from some "Founders" to round out the point in their own words.

“The Revolution was effected before the War commenced. The Revolution was in the minds and hearts of the people; a change in their religious sentiments of their duties and obligations. This radical change in the principles, opinions, sentiments, and affections of the people, was the real American Revolution.” –John Adams, 1818

"On the subject of the history of the American Revolution, you ask who shall write it ? Who can write it ? And who will ever be able to write it ? Nobody; except merely its external facts; all its councils, designs and discussions having been conducted by Congress with closed doors, and no members, as far as I know, having even made notes of them. These, which are the life and soul of history, must forever be unknown." - Thomas Jefferson to John Adams 1815

Sources: The Writings of Thomas Jefferson editor H.A. Washington New York : H.W. Derby, 1861

Joanne Freeman's Yale Course on the American Revolution, https://www.youtube.com/watch?v=shTBSGoYtK0&list=PL095301A12009E241