Chapter 1 Epigraph
Author: William Blake
Work: 'The Little Girl Lost', Songs of Innocence & Experience
The poem also describes a similar situation to that of the first chapter, "How can Lyca sleep, If her mother weep", where Lyca and Lyra are remarkably similar in name and appearance.
Not to be confused with 'A Little Girl Lost', this poem also appears in Songs of Experience. Blake often partnered his poems and as such this is linked to 'The Little Girl Found'. In this second poem, Lyca's parents meet a lion who directs them on their search - Lyra too is described in this chapter with "a tawny fairness like a lion's" (p. 4).
Chapter 2 Epigraph
Work: The Book of Job, 4:15
William Blake illustrated the Book of Job as he supposedly identified with Job due to similarly spending his life unrecognised. For more information and to see the other drawings you can check the Wikipedia article or search the Java interactive book.
You can check out the Christian hierarchy of angels here, though there are further disambiguations in the Muslim, Jewish and Zoroastrian theologies. Our understanding of the hierarchy is comes mainly from The Celestial Hierarchy, a scholarly work of the 4th or 5th century, and the work of scholoars of the Middle Ages. Informed by the New and Old Testament, these works reveal a hierarchy of three spheres, within which are three internal tiers. Each sphere has its own purpose; the first sphere are heavenly protectors, the second are heavenly governers and the third are heavenly messengers or soldiers.
Due to their purpose, the only sphere to have any interaction with man is the third, and this is why we are most familiar with them. The internal tier system is that of rulers, then archangels and finally angels. Though Pullman's hierarchy is not strictly true to this system, it is a worthy aside in understanding the human understanding of the Kingdom of Heaven's mechanisms.
Kendal Mint Cake has been used on many famous expeditions including the Antarctic explorations by Sir Ernest Shackleton and by Edmond Hillary and his team when becoming the first to reach the summit of Mount Everest. You can check out the Wikipedia article here.
Metaphysics are key to the arguments and theories explored in this novel, so for a basic guide I'd go to the ever helpful Wikipedia article.
A lot of the novel's themes of free will, space & time, and matter are all metaphysical concerns and there are many philosophers on which Pullman clearly draws. Interestingly, in the sub-article on free will, one of the main philosophers is Baruch Spinoza. The character Baruch has gone from a human (with free will) to an angel (supposedly without free will), drawing yet another interesting link in Pullman's character names.
Here's a great video that explains metaphysics - a reading from Gerardus Tros: