修改

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>图书馆</title>
</head>
<style>
input[type=text], select {
  width: 100%;
  padding: 12px 20px;
  margin: 8px 0;
  display: inline-block;
  border: 1px solid #ccc;
  border-radius: 4px;
  box-sizing: border-box;
}

input[type=submit] {
  width: 100%;
  
  color: white;
  padding: 14px 20px;
  margin: 8px 0;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}

input[type=submit]:hover {
  background-color: #45a049;
}

div {
  border-radius: 5px;
  background-color: #f2f2f2;
  padding: 20px;
}
h3{text-align:center;
  margin-top: 50px;}
</style>
<body>
<h3>修改书籍</h3>
<div>
  <form method="post">
      {% csrf_token %}

    <label for="fname">书名</label>
    <input type="text" id="fname" name="title" value ="{{info.title}}" required="required" autocomplete="off" maxlength="20">

    <label for="name">作者</label>
    <input type="text" id="name" name="name" value ="{{info.name}}" required="required" autocomplete="off" maxlength="20">

   <label for="price">价格</label>
    <input type="text" id="price" name="price" value ="{{info.price}}" required="required" autocomplete="off" maxlength="10">

    <label for="time">出版时间</label><br>
    <input type="date" id="time" name="time" value ="{{info.time}}" required="required" autocomplete="off" maxlength="20">

    <input type="submit" value="Submit">

  </form>
</div>

</body>
</html>