I didn't always agree with him but I wish him well in retirement. My biggest point is too many people try to find intellectuals that will be "everything" for them and that they will agree with.
People on the Left write him off completely, wrongly I think, because he has said things that upset their world view while people on the Right elevate him to some demigod status as if he (along with Walter Williams) are the only right thinking Blacks on the planet and we would be in a perfect position if we did everything he said. The truth is in the middle.
Sowell said some good stuff about economics and basic education and in that vein if he had focused on that and presented it in a positive light to the Black community I think progress could have been made. I think there should have been a place for him. Not necessarily in the Civil Rights organizations but special departments at HBCUs or an organization of Black intellectuals from all sides dedicated to helping us make progress. Not sure if he would have accepted that but who knows. My biggest gripe about Black conservatives isn't what they believe; I share some of their values on business, education, family, gun control, and basic freedoms. It's just they don't do anything short of write books scathing of the Black community (really, are we right in any way in their eyes?) and run for office. The OG Black conservatives like Frederick Douglass and Booker T. built institutions and businesses that inspired followers. These guys just rip into liberals which, right or wrong, is more of an ivory tower fight than actually doing work and making plans that are hard and can take time. Leadership is earned, not just demanded. I am still waiting for all those people who tell us to be self-reliant to stop working for only White controlled think tanks. Real conservative community leaders like Robert Woodson pulled out of the political conservatism when they saw it wasn't helping us.
On politics and history, I am less sanguine (and yes I have read several books, collections of his essays, and even his earliest writings in the 1960s and 1970s). While he was attacked by liberals for his stances, at times unfairly, I think his own personality and refusal to acknowledge nuance hurt him as much.
His typical response to criticism was to become more entrenched in extreme positions. He was rarely gracious to his foes, even when they were to him. William Raspberry had some good columns praising him in the 1980s in the WaPo. Unfortunately he decided to jump over to Hoover and just decided to be a full time scold on us Black masses. He once said we should get rid of HBCUs without really coming up with an alternative (he briefly attended Howard), used spurious statistics to argue since Black economic growth was faster before Civil Rights, Civil Rights weren't a big deal (hint: we were growing off a small base and some real productivity boosters like literacy helped out). He said Brown v. Board of Education was terrible since it enabled 'judicial activism'.
The biggest thing that I had a gripe with was that he almost never went against conservative orthodoxy in anything except something of specialized economics like the Laffer Curve. I mean he was even more stalwart than most White conservatives except the far right. Even when Bush started torturing folks he toed the line and told people if they weren't sure whey to vote against Bush they shouldn't or those dumb voters threatened us with a nuke terrorist attack (no hyperbole here). As much as I admire his intellect, I don't consider anyone an independent intellectual if they are that captured. The same goes for a lot of Progressive Black intellectuals.
While he did a good job in showing culture was important, his reification of it was extreme to put it lightly. He claimed nothing else mattered--not slavery, discrimination, mob violence etc. He would say since Jews, Chinese, or whoever had the right culture oppression didn't hold them back so Black people can't blame oppression for some of our issues. I won't get into the fallacies of this but when I read his books and he tried his best to magnify every bad part about Black culture and minimize any challenges we were presented with, I stayed skeptical. He actually said African culture was so deficient that we would still have been behind even if we were voluntary immigrants without slavery and segregation. I am dead serious I could pull up this quote (Commonwealth Club speech in San Fran I think). I encourage you to read his books like Race and Culture where in the first chapter he says that countries shouldn't feel bad if ethnic groups fail since it is only culture, not policies that dictate the outcome (granted he said the same about countries can't feel they are responsible for ethnic groups' successes).
Also his constant demand for "scientific evidence" in my mind became more of a rhetorical smoke screen when you really looked at his arguments in detail. His claims that affirmative action and diversity have no scientifically proven effects. There is a ream of research on affirmative action, tracking the life success of cohorts of Black kids from elite universities etc. He didn't even argue with it, he waved his hand and acted like it didn't exist. He was also fine with dispensing with scientific consensus where it didn't fit his ideology just like he accused liberals:
From this article
To commit such a basic flaw of statistics (near term fluctuations can't be predicted but long term trends are much more stable) really sank my heart. He was older at that point but to write off an entire branch of research on a fallacious statement is just wrong. Let's not get into him defending the Bell Curve as not a racist book and just a nice book outlining the behavioral differences of different populations. This isn't a Bell Curve review post but that is way off the mark.
This all being said, if you want to read books about race and the Black community, I would say you need to read some of his stuff. Even if you are just getting familiar with his arguments Race and Economics and Knowledge and Decisions are some of his better known work. I would read the Ethnic Myth by Stephen Steinberg for a counterview but Sowell makes good points.
For economics, you could read his Basic Economics but I would also read The Economists' View on the World by Stephen Rhoads to understand where he (and other economists) come from and the strength and weaknesses of this viewpoint.