Joe Friel’s The Cyclist’s Training Bible In 2021?

I have used Friels book quite extensively, I think it is still quite relevant, especially on how to put together a training schedule. I think Joe himself did say at one point that in hindsight some of the workouts were probably aimed at beginners. I find if you also use the Allan/Coggan Racing & Training with a Power Meter and get some additional ideas from that to include in your schedule it will help.

What the book doesnt really cover is the idea of polarisation if you subscribe to that school.

I find the 5 blocks to racing approach suggested by Brendan at Evoq bike very useful and I tend to use this method now which takes a classic approach to begin but gets more polarised as you get closer to the season and I put some of Hunter Allans workouts into this. He has a great series of videos on the subject, one for each block, this is the intro video (the blog is worth reading as well imo. https://www.youtube.com/watch?v=J2kpGzdNQCU&list=PLiOww7FfCwdmiWAZOfFLgJOiSgV4Xb9OW&ab_channel=EVOQ.BIKE

As per Simon's comment, it will still be relevant - the 2018 edition was only 3 years ago.

However, I don't know if it has changed since the version I bought years and years ago, as back then it was very much based on high volume training (lots of hours) and unless you're verging on Elite or doing big ultra length competition then you can be competitive on less volume. Dylan Johnson is worth checking out on YouTube as he has done a few videos on training on 6/10/16 hours a week and other training stuff.

Training and Racing with a Power Meter by Allen, Coggan and McGregor is worth a read if you have a power meter. So far as nutrition then take a look at Alan Murchison's books - they're primarily recipe books for cyclists but do have some content on how to fuel properly and when. If you can get to eating a variety of fresh un-processed foods, then I'm sure that's most of the gain right there. The rest is the final few percent. How serious are you looking to be?

I have a copy of the 4th edition published in 2009 and I'd say that it is still relevant. At 330 large (A4-ish) pages full of detail, it seems pretty comprehensive.

Despite what some people might want you to believe, the basic principles of physiology, training and fitness have not changed. Build endurance gradually, train consistently and get adequate rest, especially sleep.

Standalone diet books aren't needed IMHO. Most people will do well enough by just eating more fresh, good quality food and less junk or processed foods. I'd like to think that everyone knows what those terms mean. Be sensible with your maconutrients - more calories on heavy days, fewer on easy/rest days. Try to avoid eating late at night and eat foods with lots of micronutrients (vitamins etc). Most supplements or weird or restrictive diets seem to be mainly marketing hype. In the end there are no shortcuts. There's no magic interval that's 'the best' or wonder ingredients that can transform a big mac and fries into quality nutrition.