This article isn't for everyone. It's just for people who want to actually develop their own abilities as philosophers.
It's not an exhaustive list, but it is the list I would give my younger self as the absolute best place to start.
When I say start, what I mean is to start on the genuinely new path of Global Philosophy. To find out more about what that is, check this link.
I'll start with Western Philosophy first.
Your absolute number one port of call here is a man I continually reference, called Bryan Magee. He metabolised the entire Western Tradition.
He is a model of clarity, famed for it. His writing is crystal clear, and he never obfuscates or claims more than he knows.
The first book you want to read is called
Confessions Of A Philosopher.
It is a semi-autobiographical work that contains a crystal clear analysis and overview of the entire Western Tradition. It also gives a brilliant account of Karl Popper's work on the philosophy of science, which is instrumental to the new approach.
Once you've read that, then check out "The Great Philosophers" by the same guy, Bryan Magee.
The Great Philosophers is a set of interviews with the world's top specialists in the work of these people. Magee is just like the light cutting through the darkness here, and his ability to bring clarity to this body of work is unreal.
Once you've read that you've geared yourself up to fully appreciate his magnum opus - The Philosophy Of Schopenhauer.
It is superb.
He's written scores of books, and not a one is less than excellent, but these are the three. The reason you want to read them in this order is that by the time you finish, you will have got a crystal clear understanding of every major central idea of the Western tradition, all set in clear context, with the high-watermark of Western philosophy in clear view.
Three books to read - that's a pretty big payoff. I do recommend you do it like this - this is the advice I would give to young Ciaran had I a DeLorean equipped with a flux capacitor.
Now, Eckhart Tolle is a very different kind of writer to Magee. He's has all the flaws of an Eastern thinker - intermittent vagueness, and an occasional urge to use the word 'energy' in a way not strictly recognised by physics - but he also has this intense clarity of communication and a very stripped down way of talking about things, that I can only assume comes from his background as a Cambridge academic.
The Power Of Now is a brilliant piece. It really Westernises Zen as much as it can be Westernised without dropping the reverence. What this did for me was give me an 'in' - a clear understanding of enough of the core shape of what Eastern thought is all about that when I then came to hit the harder tomes of ancient wisdom, I wasn't just giving myself a headache. I could see far deeper into them all, and that's because of the simplicity of Tolle's insight.
He's not flawless in the way he talks about it, and his style may grate for some, but I have found nobody who can bring the insight from the Eastern tradition into as clear a focus as he.
The Eastern texts I would highly recommend that you read personally are these:
1 - The Platform Sutra. - It is basically the equivalent of the Bible, but for Zen. A tour de force. Free online.
2 - The Tao Te Ching - The one work of Lao Tze. It's up there with the most beautiful best poems ever, and it's profound to boot. Free online.
3 - The Bhaghavad Gita - This is beautiful, there's no getting away from it. Like a distillation of the Hindu Upanishads (the core basis for Indian philosophy). When you read it, really search hard to get a version that is not relentlessly embedded with some scholar giving a page of theological analysis after every paragraph. Just the Gita, thanks.
Those are probably your big three.
As for more modern pieces, it's really Advaita which has the heavy hitters. Two really rise above the crowd.
1 - Ramana Maharshi's "Be As You Are" - a collection of dialogues collated by a fellow called David Godman if memory serves. Free online on Scribd. He's very good.
2 - Nisargadatta Maharaj's "I Am That" - again, this is free online and is a collection of dialogues. This man has the patience of Job. More edge than Maharshi, not quite as cuddly. Brilliant. Free online.
That's Eastern thought. There is, however, another wisdom tradition that's far closer to home. If you're from where I'm from. Not if you're from India, or something. Obviously.
There are three pieces of Christian Philosophy which I have encountered that are genuinely magnificent. They are stunningly deep pieces, and I would recommend that you read them yourself, and find out what I mean.
1 - The Great Divorce, by C. S. Lewis. This is the book that started me on philosophy. It's incredible.
2 - The sermons of Meister Eckhart. - He's amazing. All his stuff is free online.
3 - The Gospel Of Thomas. - The person who you will meet in these sayings is very far from meek or mild. Free online.
I think that's probably enough for now. Of all the stuff I've read it's these things which have stayed with me, and which I would, with no reservation, recommend to you as the core part of your research into philosophy.