Not working if using Localized and I18n

I'm not sure I fully understand the issue (what exactly is not working? What is the error pattern?), but if the books shows up with empty pages, it might be you are using a language code as default (first language) which is different than the language of your operating system. And if you did not provide content for that language (yet), you will see empty pages.

Try to select the other language(s) to find out if any language has content.
And/or provide more details, please

<object style="visibility: visible;" data="http://localhost/en/sites/all/libraries/mz3/megazine/preloader-fat.swf" id="megazine" type="application/x-shockwave-flash" height="100%" width="100%"><param value="false" name="menu"><param value="noScale" name="scale"><param value="true" name="allowFullscreen"><param value="always" name="allowScriptAccess"><param value="#333333" name="bgColor"><param value="basePath=http://localhost/en/sites/all/libraries/mz3/megazine&amp;xmlFile=http://localhost/en/node/16/pageflip/mz3-viewer-xml" name="flashvars"></object>

If you look at the url in data, basePath and xmlFile, the language code '/en/' is the problem.

I don't know if this is a good solution but it works for me:
goto your modules folder and find: "pageflip_mz3_viewer.module" and goto rule: 419:
$absolute = array('absolute' => TRUE);
and replace it with:
$absolute = array('absolute' => TRUE,'language' => FALSE);

This gives the following warning:
Notice: Trying to get property of non-object in locale_language_url_rewrite_url()

I haven't tried to fix this warning.

Anyway the module needs to be updated I think.

I do not know the module that interfaces/integrates with MegaZine3; and I do not know Drupal.
But I know MegaZine3 ;-)

Therefore I only can be of limited help.
Regarding the language support of MegaZine3:
One of the features of MegaZine3 is the automatic support of several languages. Those languages are usually set as a book parameter (parameter 'lang', with a list of 2 letter codes fors all the languages used. Like en, es, de, it, fr, ...).
If only one language is used, the 'lang' parameter can be omitted, and for all languages that books wil be used.
But MegaZine3 does not create such path names or does anythink like URL rewrites.

The error message for me is more an indicator of a wrong configuration of Drupal (I18n, URL rewrite depending on the selected language; which probably does not work as expected). And the configuration defined with the array (key , value pairs) modifies that behavior somehow. Like as result of the error default values are choosen that luckily work.
Or soemthing like gues I'm just making an unqualified guess ;-)