Hi Gemini Mum
The Diabetes Code by Jason Fung would also be my go to book. But if your Dad has access to the internet I personally found it easier to begin with watching Jason Fung's videos on line - lots on you tube or dietdoctor.com. Also, there is a lot of free information on dietdoctor.com (no need to pay) which is written clearly.
Because lowering his carb intake is key I also found the book 'Carbs & Cals Carb & Calorie Counter: Count Your Carbs & Calories with Over 1,700 Food & Drink Photos' was useful to begin with. You can get this on Amazon or probably order in local bookshop - can only find an old link to Amazon just now.
I'm sure others will be able to suggest other books
Also, if he hasn't got access to the internet , it still might be worth someone trying to print off some of the material say from dietdoctor.com and from here. I created a paper file with different info and kept it in the kitchen.
I found the dietdoctor visual guides to foods to eat and not eat were really helpful. e.g.
https://www.dietdoctor.com/low-carb/vegetables.
Also Dr David Unwin's chart of different amounts of carbs in common foods, shown as spoonfuls of sugar which is found here;
https://phcuk.org/sugar/
and the basic diet sheet Dr Unwin gives to his patients
https://www.dietdoctor.com/wp-conte...sheet-of-what-to-eat-with-Dr.-David-Unwin.pdf