Keep at it. I hear they can be very expensive and heavily edited. You could grab this to tide you over. I have it and it's very good. https://www.amazon.com/Crystal-Lake-Memories-Complete-History/dp/1845763432/ref=pd_lpo_14_t_0/136-3272645-9170616?_encoding=UTF8&pd_rd_i=1845763432&pd_rd_r=0331ff29-07c4-42ad-941b-a5692487409a&pd_rd_w=B21kQ&pd_rd_wg=a1qEF&pf_rd...
Yeah, I've never been able to watch the whole documentary in one sitting either but that's okay.
And yes, it was originally a book by Peter Bracke filled with all sorts of interviews with the cast and crew and so many behind the scenes photos. Well worth picking up if you're a fan:
They used it as the basis for a documentary on the franchise which is available on Amazon Prime.
Just through Amazon
Crystal Lake Memories: The Complete History of Friday The 13th https://www.amazon.com/dp/1845763432/ref=cm_sw_r_cp_apa_i_NnvsEb22XDFM8