Apparently one of the things the HIStory franchise does is release novelizations (novel adaptations) of their series.

So, there's a HIStory3: Trapped 圈套 novel, which was released in mid-June a few weeks after the airing of the last episode. A digital version
is actually for sale on Google Play Books. For the low cost of about US$6 (or local equivalent), you get the novel, the two 3-years-later epilogues centering on Tang Yi/Meng Shao Fei and Jack/Zhao Zi, and some exclusive photographs not found anywhere else. Worth getting if you have a Google Play account, even if you can't read Chinese, to support Trapped.
There are translations of the novel being done by
stebeee and
weilongfu. Stebee posts them on her Tumblr,
in this master thread. So far, they're up to Chapter 7 out of 10 (not including the 2 epilogues).
While not fully translated yet, stebeee has also posted summaries of
Epilogue 1 and
Epilogue 2.
Please note that any character details revealed in the novel epilogues are considered spoilers for the purposes of this comm, and I would like to request that any discussion of said details be put under a spoiler tag until one week after the novel done being translated.

The HIStory3: Trapped 圈套 photobook
is also available for sale on Google Play Books, for US$9 or local equivalent. This is over 200 pages of high quality still photographs from the series, and again, if you have the extra cash to throw around, is an amazing source of images for icons or whatever graphics you want to make.
The two-page spreads are heavily skewed toward Tang Yi and Meng Shao Fei (as they are the A-couple),
( so you get some nice ones... )Again, worth your money if you've got a couple extra bucks to throw around.