Descent Into Madness

Two teenage inventors find themselves in over their heads against deadly creatures that lurk in the shadows. Trapped in a laboratory haunted by its own past, they find that it's more than just their lives at stake.
The battle against insanity may be more difficult than the battle to make it out alive.

First in the Insanity series but can be read as a standalone.

Credit to @-Judy- for the cover.
Credit to @_peach_bunny for editing it up to chapter five.