<p>AN EASY WAY TO CHANGE TEXT IN :HOVER AND :ACTIVE <br><br>- CSS & data attribute, no JS -</p>
<button class="button" type="button" data-hover="CLICK ME" data-active="I'M ACTIVE"><span>HOVER EFFECT</span></button>

*,
*:before,
*:after {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

body {
    text-align: center;
    background: #00C8FF;
}

p {
    font-size: 1.6em;
    font-family: 'Lato', sans-serif;
    background-color: #fff;
    padding: 1em;
    color: #002240;
    margin-top: 0;
}

/* .button */

.button {
    display: inline-block;
    position: relative;
    margin: 1em;
    padding: 0.67em;
    border: 2px solid #FFF;
    overflow: hidden;
    text-decoration: none;
    font-size: 2em;
    outline: none;
    color: #FFF;
    background: transparent;
    font-family: 'raleway', sans-serif;
}

.button span {
    -webkit-transition: 0.6s;
    -moz-transition: 0.6s;
    -o-transition: 0.6s;
    transition: 0.6s;
    -webkit-transition-delay: 0.2s;
    -moz-transition-delay: 0.2s;
    -o-transition-delay: 0.2s;
    transition-delay: 0.2s;
}

.button:before,
.button:after {
    content: '';
    position: absolute;
    top: 0.67em;
    left: 0;
    width: 100%;
    text-align: center;
    opacity: 0;
    -webkit-transition: .4s,opacity .6s;
    -moz-transition: .4s,opacity .6s;
    -o-transition: .4s,opacity .6s;
    transition: .4s,opacity .6s;
}

/* :before */

.button:before {
    content: attr(data-hover);
    -webkit-transform: translate(-150%,0);
    -moz-transform: translate(-150%,0);
    -ms-transform: translate(-150%,0);
    -o-transform: translate(-150%,0);
    transform: translate(-150%,0);
}

/* :after */

.button:after {
    content: attr(data-active);
    -webkit-transform: translate(150%,0);
    -moz-transform: translate(150%,0);
    -ms-transform: translate(150%,0);
    -o-transform: translate(150%,0);
    transform: translate(150%,0);
}

/* Span on :hover and :active */

.button:hover span,
.button:active span {
    opacity: 0;
    -webkit-transform: scale(0.3);
    -moz-transform: scale(0.3);
    -ms-transform: scale(0.3);
    -o-transform: scale(0.3);
    transform: scale(0.3);
}

/*  
    We show :before pseudo-element on :hover 
    and :after pseudo-element on :active 
*/

.button:hover:before,
.button:active:after {
    opacity: 1;
    -webkit-transform: translate(0,0);
    -moz-transform: translate(0,0);
    -ms-transform: translate(0,0);
    -o-transform: translate(0,0);
    transform: translate(0,0);
    -webkit-transition-delay: .4s;
    -moz-transition-delay: .4s;
    -o-transition-delay: .4s;
    transition-delay: .4s;
}

/* 
  We hide :before pseudo-element on :active
*/

.button:active:before {
    -webkit-transform: translate(-150%,0);
    -moz-transform: translate(-150%,0);
    -ms-transform: translate(-150%,0);
    -o-transform: translate(-150%,0);
    transform: translate(-150%,0);
    -webkit-transition-delay: 0s;
    -moz-transition-delay: 0s;
    -o-transition-delay: 0s;
    transition-delay: 0s;
}