High level description of modern Lightning network (as per BOLT) The Lightning network specification (BOLT) differs substantially from the original Lightning network paper (some of the differences outlined in this SE answer). Is there a document with a high-level technical description of the Lightning network as per BOLT? The problem I'm facing is that BOLT is a bit overwhelming, I'd like to see concepts introduced step by step (e.g., types of transactions used, the overall mechanics, etc) before the implementation details.
There is an article series on medium by rusty Russell (one of the main authors of the BOLTs) 

The first part can be found at https://medium.com/@rusty_lightning/the-bitcoin-lightning-spec-part-1-8-a7720fb1b4da and the succeeding parts are linked from there. 

This article series is from late 2016 and also somewhat outdated. 

I recently started to write a book about the lightning network at https://github.com/renepickhardt/The-Lightning-Network-Book the goal is to bridge the gap. But the book has not arrived at describing the BOLTs yet.

On a extremely high level I can tell you that the BOLTs have several components :


the peer 2 peer protocol ( messages and gossip) 
the transport protocol (onion routing and SPHINX) 
construction of payment channels via RSMCs 
transactions (RSMCs and HTLCs) 
payment process via invoices


While the structure of the BOLTs is clear they still seem to be entangled among these topics and indeed a high level overview or "architecture" seems to be missing. For example I had a hard time understanding that the transport layer and the HTLCs are two very different things. Stuff like the gossip protocol and the transport layer are pretty much not mentioned in the white paper