.book-item {
  text-align: center;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  height: 100%;
  padding: 15px;
}

.book-image {
  display: block;
  margin: 0 auto 15px auto;
  max-width: 100%;
  height: auto;
}

.book-title {
  font-weight: bold;
  margin: 10px 0 5px 0;
}

.book-meta {
  font-size: 14px;
  line-height: 1.5em;
}

.book-thumb {
  height: 220px;          /* pick a value that fits your tallest cover */
  display: flex;
  align-items: center;    /* vertical centering */
  justify-content: center;/* horizontal centering */
  margin-bottom: 15px;
}

.book-thumb img {
  max-height: 100%;
  max-width: 100%;
}