The Heart Sutra – a very brief Sutra – is Buddhism in a nutshell.
Bernie Glassman says in “The Dude and the Zen Master” that the Heart Sutra begins with the most important word “Avalokiteshvara” or even better with the letter “A”. If this “A” is wholly encompassed, the Heart Sutra is all encompassed.
So true, bearing in mind the metaphor of the jewel net of Indra – in the Avatamsaka Sutra (translated by Thomas Cleary as “The Flower Ornament Scripture”) – stating that every single glass pearl in Indra’s Net reflects the whole endless Net, and at the same time every single glass pearl shapes the whole Net.
In the same way, although the Heart Sutra is Buddhism in a nutshell, it is not so much a summary of Buddhism, this Sutra is the very core of Buddhism (as all is the very core of Buddhism).
This translation – in English – and the commentary by Red Pine is excellent, and extensive in a tiny book.