<% books.forEach(function(book){ %>
    <button onclick="getBookDetails(<%=book %>);" > <%=book.name %></button>
  <% }); %>

function getBookDetails(book){
   //using book object
}

<% books.forEach(function(book){ %>
    <button onclick="getBookDetails(<%-JSON.stringify(book)%>);"><%=book.name %></button>
<% }); %>

<% books.forEach(function(book){ %>
    <button onclick="getBookDetails('<%= JSON.stringify(book) %>')"><%= book.name %></button>
<% }) %>

function getBookDetails(bookString){
   let book = JSON.parse(bookString)
   // now you can use the book object
}