我发现导致图像溢出其容器的原因是pull-left类（声明了float: left!important）。如果删除此类，图像不会溢出，但显然，您希望文本在图像周围浮动。
但是，我能够简单地通过将图像放在p之前来解决这个问题。我不明白有什么变化，但决定继续下去，并张贴这个答案，而不是花更多的时间试图找出它。
前：<div class="newspaper"><p><img>Lorem ipsum</p></div>
后：<div class="newspaper"><img><p>Lorem ipsum</p></div>

.book {
  height: 100%;
  max-height: 100%;
  object-fit: scale-down;
  width: auto;
}
.newspaper {
  background: lightgray;
  column-count: 3;
  column-gap: 20px;
}

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.4.1/dist/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">
<h1>
  Test
</h1>
<div class="container-fluid">
  <div class="row">
    <div class="col-xs-12">
      <div class="newspaper">
        <img src="https://streissguthgardens.com/assets/Streissguth-In_Love_with_a_Hillside_Garden-e1b787f274c8c2cc3beaf52cdcba1dbee982c503ab098d558a4053702ba8d8e1.jpg" class="book img-responsive img-thumbnail pull-left" alt="Place holder text">
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Nisl tincidunt eget nullam non nisi est sit amet facilisis. Faucibus vitae aliquet nec ullamcorper sit amet risus. Urna id volutpat lacus laoreet non curabitur gravida arcu. Neque gravida in fermentum et sollicitudin. Ipsum nunc aliquet bibendum enim facilisis gravida.</p>
        <p>Congue nisi vitae suscipit tellus mauris a diam. Mus mauris vitae ultricies leo integer malesuada nunc vel. Nunc vel risus commodo viverra maecenas. Sed arcu non odio euismod lacinia at quis risus sed. Eu sem integer vitae justo eget. Lectus quam id leo in vitae. Malesuada proin libero nunc consequat interdum varius sit amet mattis. Orci phasellus egestas tellus rutrum tellus pellentesque eu tincidunt. Lectus vestibulum mattis ullamcorper velit sed ullamcorper. Id leo in vitae turpis massa sed elementum tempus. In eu mi bibendum neque egestas congue quisque egestas. Nisl pretium fusce id velit ut tortor pretium. Convallis tellus id interdum velit laoreet id donec. Sed vulputate odio ut enim. Ipsum a arcu cursus vitae congue mauris. Lectus nulla at volutpat diam ut venenatis. Morbi tristique senectus et netus et malesuada fames ac. Vel turpis nunc eget lorem dolor sed viverra ipsum nunc. Est velit egestas dui id.
        </p>
      </div>
    </div>
  </div>
</div>

我已经通过改变.book类的样式得到了它，如果你想避免图像质量的损失，我建议设置一个“最大高度”的像素。

.book {
    width: 100%;
    background: transparent;
    border: none;
    object-fit: contain;
    max-height: inherit; /* replace "inherit" with something like "250px" to avoid poor image quality on larger screens. */
}
.newspaper {
  background: lightgray;
  column-count: 3;
  column-gap: 20px;
}

<!-- 
  Bootstrap docs: https://getbootstrap.com/docs
-->
    <h1>
      Test
    </h1>
    <div class="container-fluid">
      <div class="row">
        <div class="col-xs-12">
          <div class="newspaper">
            <p><img src="https://streissguthgardens.com/assets/Streissguth-In_Love_with_a_Hillside_Garden-e1b787f274c8c2cc3beaf52cdcba1dbee982c503ab098d558a4053702ba8d8e1.jpg" class="book img-responsive img-thumbnail pull-left" alt="Place holder text">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Nisl tincidunt eget nullam non nisi est sit amet facilisis. Faucibus vitae aliquet nec ullamcorper sit amet risus. Urna id volutpat lacus laoreet non curabitur gravida arcu. Neque gravida in fermentum et sollicitudin. Ipsum nunc aliquet bibendum enim facilisis gravida.</p>
            <p>Congue nisi vitae suscipit tellus mauris a diam. Mus mauris vitae ultricies leo integer malesuada nunc vel. Nunc vel risus commodo viverra maecenas. Sed arcu non odio euismod lacinia at quis risus sed. Eu sem integer vitae justo eget. Lectus quam id leo in vitae. Malesuada proin libero nunc consequat interdum varius sit amet mattis. Orci phasellus egestas tellus rutrum tellus pellentesque eu tincidunt. Lectus vestibulum mattis ullamcorper velit sed ullamcorper. Id leo in vitae turpis massa sed elementum tempus. In eu mi bibendum neque egestas congue quisque egestas. Nisl pretium fusce id velit ut tortor pretium. Convallis tellus id interdum velit laoreet id donec. Sed vulputate odio ut enim. Ipsum a arcu cursus vitae congue mauris. Lectus nulla at volutpat diam ut venenatis. Morbi tristique senectus et netus et malesuada fames ac. Vel turpis nunc eget lorem dolor sed viverra ipsum nunc. Est velit egestas dui id.
            </p>
          </div>
        </div>
      </div>
    </div>