For me it's that far and away besteller of all time and at all times - the Bible.
It is so relevant for every situation and every age.
You want to fully understand the roots and failings and seemingly impossible resolution of the Israel / Gaza conflict ? - go to Genesis 16 and onwards. Do you know the word Hamas is used over 40 times in the Old Testament and what it means ?
You want insight into how the world is likely to be going forward - go to the first five verses of 2 Timothy 3 to get a snapshot of the current mentality, predicted over 2000 years ago, while others ( eg Luke 21) prophesy how it goes from here on in and , even though written 2000 plus years ago it talks of ' the end' as having significant climate change / events, pestilences , various conflicts and armies surrounding Israel and so on.
Looking for wisdom ? Read Solomon's wisdom in Ecclesiastes written 3000 years ago and as up to date and helpful today as ever - 'everything is meaningless, a chasing after the wind' he says repeatedly, as he looks for meaning in projects, art, wealth, women, fame and so on.
When you think of all those OT stories , there has not been one archeological find that contradicts them.
Ancient texts, thousands of years old, are discovered in caves in this period and do not contradict the texts of today.
Why ,even Dawkins is softening and called himself a ' cultural Christian' last week , lamenting the loss of Christian culture in values, in song, art and architecture and so on.
And , as always, whenever a country tries to outlaw this book ( China / Russia / Cambodia) it comes back in greater measure - the fastest growing area of demand right now ? .. Iran.
This book turns ex Khmer Rouge soldiers into servants of the people, terrorists into peace lovers, addicts into good fathers, slave traders into abolitionists and so on. Sadly a tiny minority will always misuse it, but believe me it's been seriously neglected in the last two generations and our social fabric is paying the price for that and maybe at an accelerating rate.
I can't recommend it highly enough.