Readwise and Reader
I've been a Readwise user for 4 years now and I can say without a doubt that it has been the best investment I have made towards increasing the retention of what I read.
I lost count of the times that the Daily Review brought up the exact highlight I needed in that moment, making me more effective and more content.
Their Reader is equally good and I have moved over all my feeds from Feedly as soon as it was usable. The Chrome extension lets you save pages for reading later, highlight content, etc. It's just an indispensable tool.
I'm just a satisfied, paying user and Readwise did not sponsor this content.