Fixed income investing

 The bond market changed in 2008. Before that, it was actually possible to never touch stocks and still retire.

I no longer believe that to be true. There are 2 things working against a fixed income investor:

1/ The way inflation is measured is constantly being changed. I doubt there are very many people for whom the CPI actually shows real inflation as they experience it.  It's easy to do your own research with expenses if you have just one checking account that you're pulling money from. When I tracked my expenses over the period of a few years, it was an eye opener. A 5-year TIPS got me around 20% at maturity, but expenses went up close to 50%. This is from 2019-2024. If the discrepancy between CPI and your actual experienced inflation is 50% (i.e. when CPI is 1%, you experience 1.5%), this has minimal impact at low values of CPI. The hotter that CPI runs, the bigger the impact. For example, if you have an investment that tracks the CPI and CPI is 4%, you are essentially losing 2% of purchasing power per year. And that's before taxes, which brings us to #2.

2/ Taxes are a killer with fixed income in a taxable account. With the NIIT, for someone in the 35% tax bracket, the total tax rate is 38.8%. With a 3 month t-bill earning 3.6% state tax free (this matters in a lot in states like CA that have a high state income tax), one would end up with only 2.2% after tax. Current CPI is 3.3%. So this is a guaranteed loss of purchasing power. The highest yield on the treasury curve is 4.88% for a 30 year bond. After tax that leaves 2.98%! Yes, even if one was crazy to risk capital for 30 years, they would be guaranteed losing to CPI right now, let alone actual spend which is actually much higher than 3.3%. TIPS in taxable account aren't going to be of much help, plus they come with the added disadvantage that you have to pay taxes on the inflation adjustments even without getting paid--the opposite of tax deferral! Products like BOXX may help, but they require taking added risk which I don't fully understand.

Corporate bonds are even worse because the yield spreads vs treasuries are low and they are subject to state tax. So even they don't keep up with inflation.

If a bond book was written before 2008, it is probably not very relevant for today's investing environment.  When bond investing worked, this book was probably the best book:
https://zvibodie.com/book/worry-free-investing/
You can now buy a pdf for $5 at the link above.
The gist of the book was that you only start investing in stocks when your basic retirement needs are covered by fixed income instruments (money market funds, CDs, stable value funds, treasuries, TIPS, I-Bonds, E-Bonds). This is almost impossible to achieve today as you'd be constantly falling behind.

It's OK to hold bonds. Just know that historical data that shows that it can keep up with inflation (or even exceed it) no longer holds.