My custom Google Play Theme

Google Play Books Dark Reader.css

@-moz-document url-prefix("https://play.google.com/books/reader"), url-prefix("https://books.googleusercontent.com/") {
body,
.gb-page-root,
.gb-reader-container {
  font-family: 'SF Pro Display', 'Roboto', BlinkMacSystemFont, 'Merriweather', serif;
  line-height: 1.75em;
  color: #D1D1D1;
  background-color: #222233;
}

.gb-segment > p {
  margin-top: 18px;
  margin-bottom: 18px;
}

.gb-page-wrapper-body {
  padding-left: 15px !important;
  padding-right: 15px !important;
}

.gb-statusbar {
  opacity: 0;
  transition: opacity 0.3s ease 0s;
}

.gb-statusbar:hover {
  opacity: 1;
}

.gb-topbar {
  opacity: 0;
  transition: opacity 0.3s ease 0s;
}

.gb-topbar:hover {
  opacity: 1;
}
}