Here's what Eckhart says about this book:
http://www.inner-growth.info/power_of_n ... hat_is.htm
The key of her method is based on 4 simple questions about our 'so-called' problems we see in others (our negative judgements etc ...), she calls this questioning the 'investigation':"Byron Katie's Work is a great blessing for our planet. The root cause of suffering is identification with our thoughts, the 'stories' that are continuously running through our minds. Byron Katie's Work acts like a razor-sharp sword that cuts through that illusion and enables you to know for yourself the timeless essence of your being. Joy, peace, and love emanate from it as your natural state. In Loving What Is, you have the key. Now use it." -- Eckhart Tolle, author of The Power of Now
The four questions are:
1) Is it true?
2) Can you absolutely know that it's true?
3) How do you react, what happens, when you believe that thought?
4) Who would you be without that thought?
Then a key aspect of the method consists of 'turning our judgements around' ie. instead of saying "HE should be such and such ...", it turns around as "I should be such and such ...".
So how does this simple method relate to Eckhart's teachings ?
When we say something like "this should be so and so" what does this mean ?
It means that we negate or resist to "what is" ... things as they are is the only reality ... so saying "this should be otherwise than it is" can only be untrue, false ... this is the role of the first 2 questions to see this.
And this reminds me this quote from Anais Nin:
"We don't see things as they are, we see things as WE are" ...
Then the third question is about the effect of this thought on me ? What is this effect ? ... it can only generate stress and discomfort, because I cannot fight 'what is' ... this is impossible ... what you resist persists ...
Then the last question addresses the freedom form those erroneous thoughts, when I free myself from those thoughts, then I am free from all the conflicts I did create with my own judgements and thoughts ...
Then the role of the 'turnaround' is a key aspect, why ? Because instead of saying "others should be such and such ..." (which means btw that I am a 'victim' of others), the statement becomes "I should be such and such ..." which means that the problems lie in ME and that I can now take my own responsibility for my own life ... and this frees me, because what I am does no more depend on what others say or do or think, but only on what I say or do or think ... and this is freedom ...
All we have to do is "Love what is" ...