. . The problem is that these links can be kind of "about:blank" because they are not specified in the href attribute normally, so it breaks your expected behavior when using ctrl+click, middle click or something alike. Sometimes sites links to "javascript:" pseudo-protocol, sometimes the link is for "#" with a "onclick" trigger... It depends on the situation.
. . For this specific case it's easy enough to write a user script that will rewrite these kind of links, if you're willing to use something like Tampermonkey:
// ==UserScript==
// @name       SelfLinks Fixer
// @namespace  http://dnun.es./
// @version    0.1
// @description  This script rewrites "window.open(..., '_self')" links so that you can click them as you wish.
// @match      http://libgen.info/*
// @copyright  2013, http://dnun.es.
// ==/UserScript==
var tRegExp = '^javascript: *'+
  '(window\\.)?open\\('+
  ' *(([\'"])([^\\3]+)\\3) *,'+
  ' *[\'"]_self[\'"] *'+
  '\\) *;? *$';
var fixLinksCheck = new RegExp(tRegExp);
var as = document.getElementsByTagName('a'), i = 0, n = as.length, a;
for (;i<n;i++) { a = as[i];
  if (fixLinksCheck.test(a.href)) { //damn you _self link!
    a.href = a.href.replace(fixLinksCheck, '$4');
  }
}
. . This code "fixes" only the "_self" links by changing them to normal links. You can then click them with middle button, holding ctrl/shift or whatever. It also leave the "_blank" or "_top" links untouched.