The letter

It is a well-written with discussions in details from the author - a BTC miner (now BCH miner). There are quite a few good points in it, but I will just point out some:

The author points out the flaws in the current BTC system: hostile takeovers from corporation, censored discussions in multiple forums, technical errors and potential security risks (all with references)
Redirect people to the true decentralized version of Bitcoin - Bitcoin Cash. BCH is not only developed by multiple dev teams (at least 5) but also EDA (emergency difficulty adjustment) - an important feature to help miners stabilize their profits.
A proposal for switching hashrate from Legacy BTC to BCH before / after the "Forking event 2x" mid of this November 2017.

The analysis

Currently, not only this letter but a lot of proposing strategies are being published in various forums from Reddit to Twitter to ignore this fork and focus on helping BCH. Another good analysis can be found here on Medium about which coins to put your bet on during this fork: https://medium.com/@ross.p/with-less-than-a-dozen-days-left-before-the-segwit2x-fork-i-thought-id-start-gathering-some-facts-6386fe28d84f. Some main points:

A race between both Legacy and BC2x can be a good chance for BCH (again, same as the article above) since both chains can die but not BCH ===> a dark horse. Putting your bet on BCH is actually a good move but it also means you are "taking sides" now.
Altcoins are also good buys for now! People are busy fighting each other and too much spotlights on BTC ==> No matter the outcome, money will flow back to alts once this is settled.

Conclusion

So what can you do? Here are my opinions in the "risk" order, but you can do all 3 moves

High risk Ride the BTC waves until near fork (3 - 4 days) then jump on either BCH or alts
Medium risk Stack up BCH in case it overthrown BTC after fork (keep a few... just in case it booms to 5000$)
Low risk Fill your bag of alts after jumping out of BTC's ride

Cheers